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locking/refcount: Consolidate implementations of refcount_t
The generic implementation of refcount_t should be good enough for everybody, so remove ARCH_HAS_REFCOUNT and REFCOUNT_FULL entirely, leaving the generic implementation enabled unconditionally. Signed-off-by: Will Deacon <will@kernel.org> Reviewed-by: Ard Biesheuvel <ardb@kernel.org> Acked-by: Kees Cook <keescook@chromium.org> Tested-by: Hanjun Guo <guohanjun@huawei.com> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Elena Reshetova <elena.reshetova@intel.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: https://lkml.kernel.org/r/20191121115902.2551-9-will@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Will Deacon
Ingo Molnar
parent
65b0085524
commit
fb041bb7c0
11 changed files with 59 additions and 308 deletions
21
arch/Kconfig
21
arch/Kconfig
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@ -892,27 +892,6 @@ config STRICT_MODULE_RWX
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config ARCH_HAS_PHYS_TO_DMA
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bool
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config ARCH_HAS_REFCOUNT
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bool
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help
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An architecture selects this when it has implemented refcount_t
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using open coded assembly primitives that provide an optimized
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refcount_t implementation, possibly at the expense of some full
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refcount state checks of CONFIG_REFCOUNT_FULL=y.
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The refcount overflow check behavior, however, must be retained.
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Catching overflows is the primary security concern for protecting
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against bugs in reference counts.
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config REFCOUNT_FULL
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bool "Perform full reference count validation at the expense of speed"
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help
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Enabling this switches the refcounting infrastructure from a fast
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unchecked atomic_t implementation to a fully state checked
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implementation, which can be (slightly) slower but provides protections
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against various use-after-free conditions that can be used in
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security flaw exploits.
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config HAVE_ARCH_COMPILER_H
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bool
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help
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@ -117,7 +117,6 @@ config ARM
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select OLD_SIGSUSPEND3
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select PCI_SYSCALL if PCI
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select PERF_USE_VMALLOC
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select REFCOUNT_FULL
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select RTC_LIB
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select SYS_SUPPORTS_APM_EMULATION
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# Above selects are sorted alphabetically; please add new ones
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@ -181,7 +181,6 @@ config ARM64
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select PCI_SYSCALL if PCI
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select POWER_RESET
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select POWER_SUPPLY
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select REFCOUNT_FULL
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select SPARSE_IRQ
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select SWIOTLB
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select SYSCTL_EXCEPTION_TRACE
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@ -62,7 +62,6 @@ CONFIG_OPROFILE=m
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CONFIG_KPROBES=y
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CONFIG_JUMP_LABEL=y
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CONFIG_STATIC_KEYS_SELFTEST=y
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CONFIG_REFCOUNT_FULL=y
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CONFIG_LOCK_EVENT_COUNTS=y
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CONFIG_MODULES=y
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CONFIG_MODULE_FORCE_LOAD=y
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@ -73,7 +73,6 @@ config X86
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select ARCH_HAS_PMEM_API if X86_64
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select ARCH_HAS_PTE_DEVMAP if X86_64
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select ARCH_HAS_PTE_SPECIAL
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select ARCH_HAS_REFCOUNT
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select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
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select ARCH_HAS_UACCESS_MCSAFE if X86_64 && X86_MCE
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select ARCH_HAS_SET_MEMORY
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@ -139,9 +139,6 @@
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# define _ASM_EXTABLE_EX(from, to) \
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_ASM_EXTABLE_HANDLE(from, to, ex_handler_ext)
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# define _ASM_EXTABLE_REFCOUNT(from, to) \
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_ASM_EXTABLE_HANDLE(from, to, ex_handler_refcount)
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# define _ASM_NOKPROBE(entry) \
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.pushsection "_kprobe_blacklist","aw" ; \
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_ASM_ALIGN ; \
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@ -170,9 +167,6 @@
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# define _ASM_EXTABLE_EX(from, to) \
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_ASM_EXTABLE_HANDLE(from, to, ex_handler_ext)
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# define _ASM_EXTABLE_REFCOUNT(from, to) \
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_ASM_EXTABLE_HANDLE(from, to, ex_handler_refcount)
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/* For C file, we already have NOKPROBE_SYMBOL macro */
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#endif
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@ -1,126 +0,0 @@
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#ifndef __ASM_X86_REFCOUNT_H
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#define __ASM_X86_REFCOUNT_H
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/*
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* x86-specific implementation of refcount_t. Based on PAX_REFCOUNT from
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* PaX/grsecurity.
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*/
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#include <linux/refcount.h>
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#include <asm/bug.h>
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/*
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* This is the first portion of the refcount error handling, which lives in
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* .text.unlikely, and is jumped to from the CPU flag check (in the
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* following macros). This saves the refcount value location into CX for
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* the exception handler to use (in mm/extable.c), and then triggers the
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* central refcount exception. The fixup address for the exception points
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* back to the regular execution flow in .text.
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*/
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#define _REFCOUNT_EXCEPTION \
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".pushsection .text..refcount\n" \
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"111:\tlea %[var], %%" _ASM_CX "\n" \
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"112:\t" ASM_UD2 "\n" \
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ASM_UNREACHABLE \
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".popsection\n" \
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"113:\n" \
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_ASM_EXTABLE_REFCOUNT(112b, 113b)
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/* Trigger refcount exception if refcount result is negative. */
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#define REFCOUNT_CHECK_LT_ZERO \
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"js 111f\n\t" \
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_REFCOUNT_EXCEPTION
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/* Trigger refcount exception if refcount result is zero or negative. */
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#define REFCOUNT_CHECK_LE_ZERO \
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"jz 111f\n\t" \
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REFCOUNT_CHECK_LT_ZERO
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/* Trigger refcount exception unconditionally. */
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#define REFCOUNT_ERROR \
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"jmp 111f\n\t" \
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_REFCOUNT_EXCEPTION
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static __always_inline void refcount_add(unsigned int i, refcount_t *r)
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{
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asm volatile(LOCK_PREFIX "addl %1,%0\n\t"
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REFCOUNT_CHECK_LT_ZERO
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: [var] "+m" (r->refs.counter)
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: "ir" (i)
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: "cc", "cx");
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}
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static __always_inline void refcount_inc(refcount_t *r)
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{
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asm volatile(LOCK_PREFIX "incl %0\n\t"
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REFCOUNT_CHECK_LT_ZERO
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: [var] "+m" (r->refs.counter)
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: : "cc", "cx");
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}
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static __always_inline void refcount_dec(refcount_t *r)
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{
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asm volatile(LOCK_PREFIX "decl %0\n\t"
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REFCOUNT_CHECK_LE_ZERO
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: [var] "+m" (r->refs.counter)
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: : "cc", "cx");
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}
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static __always_inline __must_check
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bool refcount_sub_and_test(unsigned int i, refcount_t *r)
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{
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bool ret = GEN_BINARY_SUFFIXED_RMWcc(LOCK_PREFIX "subl",
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REFCOUNT_CHECK_LT_ZERO,
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r->refs.counter, e, "er", i, "cx");
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if (ret) {
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smp_acquire__after_ctrl_dep();
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return true;
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}
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return false;
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}
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static __always_inline __must_check bool refcount_dec_and_test(refcount_t *r)
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{
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bool ret = GEN_UNARY_SUFFIXED_RMWcc(LOCK_PREFIX "decl",
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REFCOUNT_CHECK_LT_ZERO,
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r->refs.counter, e, "cx");
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if (ret) {
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smp_acquire__after_ctrl_dep();
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return true;
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}
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return false;
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}
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static __always_inline __must_check
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bool refcount_add_not_zero(unsigned int i, refcount_t *r)
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{
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int c, result;
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c = atomic_read(&(r->refs));
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do {
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if (unlikely(c == 0))
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return false;
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result = c + i;
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/* Did we try to increment from/to an undesirable state? */
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if (unlikely(c < 0 || c == INT_MAX || result < c)) {
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asm volatile(REFCOUNT_ERROR
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: : [var] "m" (r->refs.counter)
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: "cc", "cx");
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break;
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}
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} while (!atomic_try_cmpxchg(&(r->refs), &c, result));
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return c != 0;
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}
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static __always_inline __must_check bool refcount_inc_not_zero(refcount_t *r)
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{
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return refcount_add_not_zero(1, r);
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}
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#endif
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@ -44,55 +44,6 @@ __visible bool ex_handler_fault(const struct exception_table_entry *fixup,
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}
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EXPORT_SYMBOL_GPL(ex_handler_fault);
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/*
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* Handler for UD0 exception following a failed test against the
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* result of a refcount inc/dec/add/sub.
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*/
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__visible bool ex_handler_refcount(const struct exception_table_entry *fixup,
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struct pt_regs *regs, int trapnr,
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unsigned long error_code,
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unsigned long fault_addr)
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{
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/* First unconditionally saturate the refcount. */
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*(int *)regs->cx = INT_MIN / 2;
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/*
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* Strictly speaking, this reports the fixup destination, not
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* the fault location, and not the actually overflowing
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* instruction, which is the instruction before the "js", but
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* since that instruction could be a variety of lengths, just
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* report the location after the overflow, which should be close
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* enough for finding the overflow, as it's at least back in
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* the function, having returned from .text.unlikely.
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*/
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regs->ip = ex_fixup_addr(fixup);
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/*
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* This function has been called because either a negative refcount
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* value was seen by any of the refcount functions, or a zero
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* refcount value was seen by refcount_dec().
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*
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* If we crossed from INT_MAX to INT_MIN, OF (Overflow Flag: result
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* wrapped around) will be set. Additionally, seeing the refcount
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* reach 0 will set ZF (Zero Flag: result was zero). In each of
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* these cases we want a report, since it's a boundary condition.
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* The SF case is not reported since it indicates post-boundary
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* manipulations below zero or above INT_MAX. And if none of the
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* flags are set, something has gone very wrong, so report it.
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*/
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if (regs->flags & (X86_EFLAGS_OF | X86_EFLAGS_ZF)) {
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bool zero = regs->flags & X86_EFLAGS_ZF;
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refcount_error_report(regs, zero ? "hit zero" : "overflow");
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} else if ((regs->flags & X86_EFLAGS_SF) == 0) {
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/* Report if none of OF, ZF, nor SF are set. */
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refcount_error_report(regs, "unexpected saturation");
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}
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return true;
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}
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EXPORT_SYMBOL(ex_handler_refcount);
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/*
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* Handler for when we fail to restore a task's FPU state. We should never get
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* here because the FPU state of a task using the FPU (task->thread.fpu.state)
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@ -22,7 +22,6 @@ config DRM_I915_DEBUG
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depends on DRM_I915
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select DEBUG_FS
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select PREEMPT_COUNT
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select REFCOUNT_FULL
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select I2C_CHARDEV
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select STACKDEPOT
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select DRM_DP_AUX_CHARDEV
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@ -1,64 +1,4 @@
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/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_REFCOUNT_H
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#define _LINUX_REFCOUNT_H
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#include <linux/atomic.h>
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#include <linux/compiler.h>
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#include <linux/limits.h>
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#include <linux/spinlock_types.h>
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struct mutex;
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/**
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* struct refcount_t - variant of atomic_t specialized for reference counts
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* @refs: atomic_t counter field
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*
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* The counter saturates at REFCOUNT_SATURATED and will not move once
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* there. This avoids wrapping the counter and causing 'spurious'
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* use-after-free bugs.
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*/
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typedef struct refcount_struct {
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atomic_t refs;
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} refcount_t;
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#define REFCOUNT_INIT(n) { .refs = ATOMIC_INIT(n), }
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#define REFCOUNT_MAX INT_MAX
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#define REFCOUNT_SATURATED (INT_MIN / 2)
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enum refcount_saturation_type {
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REFCOUNT_ADD_NOT_ZERO_OVF,
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REFCOUNT_ADD_OVF,
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REFCOUNT_ADD_UAF,
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REFCOUNT_SUB_UAF,
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REFCOUNT_DEC_LEAK,
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};
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void refcount_warn_saturate(refcount_t *r, enum refcount_saturation_type t);
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/**
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* refcount_set - set a refcount's value
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* @r: the refcount
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* @n: value to which the refcount will be set
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*/
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static inline void refcount_set(refcount_t *r, int n)
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{
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atomic_set(&r->refs, n);
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}
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/**
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* refcount_read - get a refcount's value
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* @r: the refcount
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*
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* Return: the refcount's value
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*/
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static inline unsigned int refcount_read(const refcount_t *r)
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{
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return atomic_read(&r->refs);
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}
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#ifdef CONFIG_REFCOUNT_FULL
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#include <linux/bug.h>
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/*
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* Variant of atomic_t specialized for reference counts.
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*
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@ -136,6 +76,64 @@ static inline unsigned int refcount_read(const refcount_t *r)
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*
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*/
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#ifndef _LINUX_REFCOUNT_H
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#define _LINUX_REFCOUNT_H
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#include <linux/atomic.h>
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#include <linux/bug.h>
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#include <linux/compiler.h>
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#include <linux/limits.h>
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#include <linux/spinlock_types.h>
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struct mutex;
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/**
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* struct refcount_t - variant of atomic_t specialized for reference counts
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* @refs: atomic_t counter field
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*
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* The counter saturates at REFCOUNT_SATURATED and will not move once
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* there. This avoids wrapping the counter and causing 'spurious'
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* use-after-free bugs.
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*/
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typedef struct refcount_struct {
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atomic_t refs;
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} refcount_t;
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#define REFCOUNT_INIT(n) { .refs = ATOMIC_INIT(n), }
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#define REFCOUNT_MAX INT_MAX
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#define REFCOUNT_SATURATED (INT_MIN / 2)
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enum refcount_saturation_type {
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REFCOUNT_ADD_NOT_ZERO_OVF,
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REFCOUNT_ADD_OVF,
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REFCOUNT_ADD_UAF,
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REFCOUNT_SUB_UAF,
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REFCOUNT_DEC_LEAK,
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};
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void refcount_warn_saturate(refcount_t *r, enum refcount_saturation_type t);
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/**
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* refcount_set - set a refcount's value
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* @r: the refcount
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* @n: value to which the refcount will be set
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*/
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static inline void refcount_set(refcount_t *r, int n)
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{
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atomic_set(&r->refs, n);
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}
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/**
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* refcount_read - get a refcount's value
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* @r: the refcount
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*
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* Return: the refcount's value
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*/
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static inline unsigned int refcount_read(const refcount_t *r)
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{
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return atomic_read(&r->refs);
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}
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/**
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* refcount_add_not_zero - add a value to a refcount unless it is 0
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* @i: the value to add to the refcount
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@ -298,46 +296,6 @@ static inline void refcount_dec(refcount_t *r)
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if (unlikely(atomic_fetch_sub_release(1, &r->refs) <= 1))
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refcount_warn_saturate(r, REFCOUNT_DEC_LEAK);
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}
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#else /* CONFIG_REFCOUNT_FULL */
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# ifdef CONFIG_ARCH_HAS_REFCOUNT
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# include <asm/refcount.h>
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# else
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static inline __must_check bool refcount_add_not_zero(int i, refcount_t *r)
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{
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return atomic_add_unless(&r->refs, i, 0);
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}
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static inline void refcount_add(int i, refcount_t *r)
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{
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atomic_add(i, &r->refs);
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}
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static inline __must_check bool refcount_inc_not_zero(refcount_t *r)
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{
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return atomic_add_unless(&r->refs, 1, 0);
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}
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static inline void refcount_inc(refcount_t *r)
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{
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atomic_inc(&r->refs);
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}
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static inline __must_check bool refcount_sub_and_test(int i, refcount_t *r)
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{
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return atomic_sub_and_test(i, &r->refs);
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}
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static inline __must_check bool refcount_dec_and_test(refcount_t *r)
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{
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return atomic_dec_and_test(&r->refs);
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}
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static inline void refcount_dec(refcount_t *r)
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{
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atomic_dec(&r->refs);
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}
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# endif /* !CONFIG_ARCH_HAS_REFCOUNT */
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#endif /* !CONFIG_REFCOUNT_FULL */
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||||
|
||||
extern __must_check bool refcount_dec_if_one(refcount_t *r);
|
||||
extern __must_check bool refcount_dec_not_one(refcount_t *r);
|
||||
|
|
|
|||
|
|
@ -1,6 +1,6 @@
|
|||
// SPDX-License-Identifier: GPL-2.0
|
||||
/*
|
||||
* Out-of-line refcount functions common to all refcount implementations.
|
||||
* Out-of-line refcount functions.
|
||||
*/
|
||||
|
||||
#include <linux/mutex.h>
|
||||
|
|
|
|||
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Reference in a new issue