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sysctl.c: fix underflow value setting risk in vm_table

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Apart from subsystem specific .proc_handler handler, all ctl_tables with
extra1 and extra2 members set should use proc_dointvec_minmax instead of
proc_dointvec, or the limit set in extra* never work and potentially echo
underflow values(negative numbers) is likely make system unstable.

Especially vfs_cache_pressure and zone_reclaim_mode, -1 is apparently not
a valid value, but we can set to them.  And then kernel may crash.

# echo -1 > /proc/sys/vm/vfs_cache_pressure

Link: https://lkml.kernel.org/r/20201223105535.2875-1-linf@wangsu.com
Signed-off-by: Lin Feng <linf@wangsu.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Lin Feng 2021-02-25 17:20:53 -08:00 committed by Linus Torvalds
parent 4508943794
commit 3b3376f222
1 changed files with 4 additions and 4 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

8
kernel/sysctl.c
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@ -2962,7 +2962,7 @@ static struct ctl_table vm_table[] = {
.data = &block_dump, .data = &block_dump,
.maxlen = sizeof(block_dump), .maxlen = sizeof(block_dump),
.mode = 0644, .mode = 0644,
.proc_handler = proc_dointvec, .proc_handler = proc_dointvec_minmax,
.extra1 = SYSCTL_ZERO, .extra1 = SYSCTL_ZERO,
}, },
{ {
@ -2970,7 +2970,7 @@ static struct ctl_table vm_table[] = {
.data = &sysctl_vfs_cache_pressure, .data = &sysctl_vfs_cache_pressure,
.maxlen = sizeof(sysctl_vfs_cache_pressure), .maxlen = sizeof(sysctl_vfs_cache_pressure),
.mode = 0644, .mode = 0644,
.proc_handler = proc_dointvec, .proc_handler = proc_dointvec_minmax,
.extra1 = SYSCTL_ZERO, .extra1 = SYSCTL_ZERO,
}, },
#if defined(HAVE_ARCH_PICK_MMAP_LAYOUT) || \ #if defined(HAVE_ARCH_PICK_MMAP_LAYOUT) || \
@ -2980,7 +2980,7 @@ static struct ctl_table vm_table[] = {
.data = &sysctl_legacy_va_layout, .data = &sysctl_legacy_va_layout,
.maxlen = sizeof(sysctl_legacy_va_layout), .maxlen = sizeof(sysctl_legacy_va_layout),
.mode = 0644, .mode = 0644,
.proc_handler = proc_dointvec, .proc_handler = proc_dointvec_minmax,
.extra1 = SYSCTL_ZERO, .extra1 = SYSCTL_ZERO,
}, },
#endif #endif
@ -2990,7 +2990,7 @@ static struct ctl_table vm_table[] = {
.data = &node_reclaim_mode, .data = &node_reclaim_mode,
.maxlen = sizeof(node_reclaim_mode), .maxlen = sizeof(node_reclaim_mode),
.mode = 0644, .mode = 0644,
.proc_handler = proc_dointvec, .proc_handler = proc_dointvec_minmax,
.extra1 = SYSCTL_ZERO, .extra1 = SYSCTL_ZERO,
}, },
{ {