From: Pedro Falcato <pedro.falcato@xxxxxxxxx> commit e46bc2e7eb90a370bc27fa2fd98cb8251e7da1ec upstream. is_madv_discard did its check wrong. MADV_ flags are not bitwise, they're normal sequential numbers. So, for instance: behavior & (/* ... */ | MADV_REMOVE) tagged both MADV_REMOVE and MADV_RANDOM (bit 0 set) as discard operations. As a result the kernel could erroneously block certain madvises (e.g MADV_RANDOM or MADV_HUGEPAGE) on sealed VMAs due to them sharing bits with blocked MADV operations (e.g REMOVE or WIPEONFORK). This is obviously incorrect, so use a switch statement instead. Link: https://lkml.kernel.org/r/20240807173336.2523757-1-pedro.falcato@xxxxxxxxx Link: https://lkml.kernel.org/r/20240807173336.2523757-2-pedro.falcato@xxxxxxxxx Fixes: 8be7258aad44 ("mseal: add mseal syscall") Signed-off-by: Pedro Falcato <pedro.falcato@xxxxxxxxx> Tested-by: Jeff Xu <jeffxu@xxxxxxxxxxxx> Reviewed-by: Jeff Xu <jeffxu@xxxxxxxxxxxx> Cc: Kees Cook <kees@xxxxxxxxxx> Cc: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx> Cc: Shuah Khan <shuah@xxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- mm/mseal.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/mm/mseal.c b/mm/mseal.c index bf783bba8ed0..15bba28acc00 100644 --- a/mm/mseal.c +++ b/mm/mseal.c @@ -40,9 +40,17 @@ static bool can_modify_vma(struct vm_area_struct *vma) static bool is_madv_discard(int behavior) { - return behavior & - (MADV_FREE | MADV_DONTNEED | MADV_DONTNEED_LOCKED | - MADV_REMOVE | MADV_DONTFORK | MADV_WIPEONFORK); + switch (behavior) { + case MADV_FREE: + case MADV_DONTNEED: + case MADV_DONTNEED_LOCKED: + case MADV_REMOVE: + case MADV_DONTFORK: + case MADV_WIPEONFORK: + return true; + } + + return false; } static bool is_ro_anon(struct vm_area_struct *vma) -- 2.46.0 Patches currently in stable-queue which might be from pedro.falcato@xxxxxxxxx are queue-6.10/mseal-fix-is_madv_discard.patch
