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ANDROID: 16K: Fixup padding vm_flags bits on VMA splits

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In some cases VMAs are split without the mmap write lock held;
later the lock is taken to fixup vm_flags of the original VMA.
Since some uppper bits of vm_flags are used to encode the ELF
padding ranges, they need to be modified on splits. This is
usually handled correctly by __split_vma(). However in the above
case, the flags get over witten later under the write lock.

Preserve vm_flag bits on reset to correctly represent padding.

Bug: 357901498
Change-Id: I1cb75419e614791a47cbdb0341373f619daf0bf2
Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
This commit is contained in:
Kalesh Singh 2024-09-24 23:34:05 +00:00
parent 7b43073a77
commit 4e714a2053
3 changed files with 7 additions and 2 deletions
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5
include/linux/mm.h
View File

@ -27,6 +27,7 @@
#include <linux/sizes.h>
#include <linux/sched.h>
#include <linux/pgtable.h>
#include <linux/pgsize_migration_inline.h>
#include <linux/kasan.h>
#include <linux/page_pinner.h>
#include <linux/memremap.h>
@ -844,6 +845,8 @@ static inline void vm_flags_reset(struct vm_area_struct *vma,
vm_flags_t flags)
{
vma_assert_write_locked(vma);
/* Preserve padding flags */
flags = vma_pad_fixup_flags(vma, flags);
vm_flags_init(vma, flags);
}
@ -851,6 +854,8 @@ static inline void vm_flags_reset_once(struct vm_area_struct *vma,
vm_flags_t flags)
{
vma_assert_write_locked(vma);
/* Preserve padding flags */
flags = vma_pad_fixup_flags(vma, flags);
WRITE_ONCE(ACCESS_PRIVATE(vma, __vm_flags), flags);
}

2
mm/mlock.c
View File

@ -533,7 +533,7 @@ success:
if ((newflags & VM_LOCKED) && (oldflags & VM_LOCKED)) {
/* No work to do, and mlocking twice would be wrong */
vma_start_write(vma);
vm_flags_reset(vma, vma_pad_fixup_flags(vma, newflags));
vm_flags_reset(vma, newflags);
} else {
mlock_vma_pages_range(vma, start, end, newflags);
}

2
mm/mprotect.c
View File

@ -661,7 +661,7 @@ success:
* held in write mode.
*/
vma_start_write(vma);
vm_flags_reset(vma, vma_pad_fixup_flags(vma, newflags));
vm_flags_reset(vma, newflags);
if (vma_wants_manual_pte_write_upgrade(vma))
mm_cp_flags |= MM_CP_TRY_CHANGE_WRITABLE;
vma_set_page_prot(vma);