From dd83609b88986f4add37c0871c3434310652ebd5 Mon Sep 17 00:00:00 2001 From: Deepanshu Kartikey Date: Fri, 26 Sep 2025 09:02:54 +0530 Subject: [PATCH] hugetlbfs: skip VMAs without shareable locks in hugetlb_vmdelete_list MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 using goto to ensure locks acquired by trylock are always released, even when skipping VMAs without shareable locks. Link: https://lkml.kernel.org/r/20250926033255.10930-1-kartikey406@gmail.com Fixes: 40549ba8f8e0 ("hugetlb: use new vma_lock for pmd sharing synchronization") Signed-off-by: Deepanshu Kartikey Reported-by: syzbot+f26d7c75c26ec19790e7@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=f26d7c75c26ec19790e7 Suggested-by: Andrew Morton Cc: David Hildenbrand Cc: Muchun Song Cc: Oscar Salvador Signed-off-by: Andrew Morton --- fs/hugetlbfs/inode.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c index 3cfdf4091001f..94b4d854429e5 100644 --- a/fs/hugetlbfs/inode.c +++ b/fs/hugetlbfs/inode.c @@ -478,6 +478,14 @@ hugetlb_vmdelete_list(struct rb_root_cached *root, pgoff_t start, pgoff_t end, if (!hugetlb_vma_trylock_write(vma)) continue; + /* + * Skip VMAs without shareable locks. Per the design in commit + * 40549ba8f8e0, these will be handled by remove_inode_hugepages() + * called after this function with proper locking. + */ + if (!__vma_shareable_lock(vma)) + goto skip; + v_start = vma_offset_start(vma, start); v_end = vma_offset_end(vma, end); @@ -488,6 +496,7 @@ hugetlb_vmdelete_list(struct rb_root_cached *root, pgoff_t start, pgoff_t end, * vmas. Therefore, lock is not held when calling * unmap_hugepage_range for private vmas. */ +skip: hugetlb_vma_unlock_write(vma); } } -- 2.47.3