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x86/fault: Bypass no_context() for implicit kernel faults from usermode

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Drop an indentation level and remove the last user_mode(regs) == true
caller of no_context() by directly OOPSing for implicit kernel faults
from usermode.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/6e3d1129494a8de1e59d28012286e3a292a2296e.1612924255.git.luto@kernel.org
This commit is contained in:
Andy Lutomirski 2021-02-09 18:33:42 -08:00 committed by Borislav Petkov
parent 2cc624b0a7
commit 5042d40a26
1 changed files with 40 additions and 35 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

75
arch/x86/mm/fault.c
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@ -826,44 +826,49 @@ __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
{
struct task_struct *tsk = current;
/* User mode accesses just cause a SIGSEGV */
if (user_mode(regs) && (error_code & X86_PF_USER)) {
/*
* It's possible to have interrupts off here:
*/
local_irq_enable();
/*
* Valid to do another page fault here because this one came
* from user space:
*/
if (is_prefetch(regs, error_code, address))
return;
if (is_errata100(regs, address))
return;
sanitize_error_code(address, &error_code);
if (fixup_vdso_exception(regs, X86_TRAP_PF, error_code, address))
return;
if (likely(show_unhandled_signals))
show_signal_msg(regs, error_code, address, tsk);
set_signal_archinfo(address, error_code);
if (si_code == SEGV_PKUERR)
force_sig_pkuerr((void __user *)address, pkey);
force_sig_fault(SIGSEGV, si_code, (void __user *)address);
local_irq_disable();
if (!user_mode(regs)) {
no_context(regs, error_code, address, pkey, si_code);
return;
}
no_context(regs, error_code, address, SIGSEGV, si_code);
if (!(error_code & X86_PF_USER)) {
/* Implicit user access to kernel memory -- just oops */
page_fault_oops(regs, error_code, address);
return;
}
/*
* User mode accesses just cause a SIGSEGV.
* It's possible to have interrupts off here:
*/
local_irq_enable();
/*
* Valid to do another page fault here because this one came
* from user space:
*/
if (is_prefetch(regs, error_code, address))
return;
if (is_errata100(regs, address))
return;
sanitize_error_code(address, &error_code);
if (fixup_vdso_exception(regs, X86_TRAP_PF, error_code, address))
return;
if (likely(show_unhandled_signals))
show_signal_msg(regs, error_code, address, tsk);
set_signal_archinfo(address, error_code);
if (si_code == SEGV_PKUERR)
force_sig_pkuerr((void __user *)address, pkey);
force_sig_fault(SIGSEGV, si_code, (void __user *)address);
local_irq_disable();
}
static noinline void