hugetlb_vmdelete_list() uses trylock to acquire VMA locks during truncate
operations. As per the original design in commit 40549ba8f8e0 ("hugetlb:
use new vma_lock for pmd sharing synchronization"), if the trylock fails
or the VMA has no lock, it should skip that VMA. Any remaining mapped
pages are handled by remove_inode_hugepages() which is called after
hugetlb_vmdelete_list() and uses proper lock ordering to guarantee
unmapping success.
Currently, when hugetlb_vma_trylock_write() returns success (1) for VMAs
without shareable locks, the code proceeds to call unmap_hugepage_range().
This causes assertion failures in huge_pmd_unshare() → hugetlb_vma_assert_locked()
because no lock is actually held:
WARNING: CPU: 1 PID: 6594 Comm: syz.0.28 Not tainted
Call Trace:
hugetlb_vma_assert_locked+0x1dd/0x250
huge_pmd_unshare+0x2c8/0x540
__unmap_hugepage_range+0x6e3/0x1aa0
unmap_hugepage_range+0x32e/0x410
hugetlb_vmdelete_list+0x189/0x1f0
Fix by explicitly skipping VMAs without shareable locks after trylock
succeeds, consistent with the original design where such VMAs are
deferred to remove_inode_hugepages() for proper handling.
Reported-by: syzbot+f26d7c75c26ec19790e7@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?extid=f26d7c75c26ec19790e7
Fixes: 40549ba8f8e0 ("hugetlb: use new vma_lock for pmd sharing synchronization")
Tested-by: syzbot+f26d7c75c26ec19790e7@syzkaller.appspotmail.com
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
---
fs/hugetlbfs/inode.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 9e0625167517..9ba98cab3388 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -487,7 +487,8 @@ hugetlb_vmdelete_list(struct rb_root_cached *root, pgoff_t start, pgoff_t end,
if (!hugetlb_vma_trylock_write(vma))
continue;
-
+ if (!__vma_shareable_lock(vma))
+ continue;
v_start = vma_offset_start(vma, start);
v_end = vma_offset_end(vma, end);
--
2.43.0