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ANDROID: look up vma under RCU in linker_ctx()

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madvise_dontneed_single_vma() calls linker_ctx() to detect whether the
madvise was initiated by the dynamic linker. This function requires
mmap_lock in order to lookup the vma, however with recent changes we
do not hold mmap_lock while executing MADV_DONTNEED. Lookup the vma
under RCU instead to avoid lockdep warning.

Bug: 425827225
Change-Id: Ie5e0243f359b96292d4f32ee3299050b871dc6c5
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
This commit is contained in:
Suren Baghdasaryan
2025-06-26 20:10:38 +00:00
parent aeb35eb6f2
commit 75a0fcbfdf
1 changed files with 7 additions and 6 deletions
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13
mm/pgsize_migration.c
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@@ -167,8 +167,6 @@ static __always_inline bool str_has_suffix(const char *str, const char *suffix)
* VMAs of the current task.
*
* Returns true if in linker context, otherwise false.
*
* Caller must hold mmap lock in read mode.
*/
static inline bool linker_ctx(void)
{
@@ -180,14 +178,14 @@ static inline bool linker_ctx(void)
if (!regs)
return false;
vma = find_vma(mm, instruction_pointer(regs));
vma = lock_vma_under_rcu(mm, instruction_pointer(regs));
/* Current execution context, the VMA must be present */
BUG_ON(!vma);
file = vma->vm_file;
if (!file)
return false;
goto out;
if ((vma->vm_flags & VM_EXEC)) {
char buf[64];
@@ -205,10 +203,13 @@ static inline bool linker_ctx(void)
*
* Check the base name (linker64).
*/
if (!strcmp(kbasename(path), "linker64"))
if (!strcmp(kbasename(path), "linker64")) {
vma_end_read(vma);
return true;
}
}
out:
vma_end_read(vma);
return false;
}