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nilfs2: fix general protection fault in nilfs_lookup_dirty_data_buffers()

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A syzbot stress test reported that create_empty_buffers() called from
nilfs_lookup_dirty_data_buffers() can cause a general protection fault.

Analysis using its reproducer revealed that the back reference "mapping"
from a page/folio has been changed to NULL after dirty page/folio gang
lookup in nilfs_lookup_dirty_data_buffers().

Fix this issue by excluding pages/folios from being collected if, after
acquiring a lock on each page/folio, its back reference "mapping" differs
from the pointer to the address space struct that held the page/folio.

Link: https://lkml.kernel.org/r/20230805132038.6435-1-konishi.ryusuke@gmail.com
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Reported-by: syzbot+0ad741797f4565e7e2d2@syzkaller.appspotmail.com
Closes: https://lkml.kernel.org/r/0000000000002930a705fc32b231@google.com
Tested-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Ryusuke Konishi 2023-08-05 22:20:38 +09:00 committed by Andrew Morton
parent 5805192c7b
commit f83913f8c5
1 changed files with 5 additions and 0 deletions
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5
fs/nilfs2/segment.c
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@ -725,6 +725,11 @@ static size_t nilfs_lookup_dirty_data_buffers(struct inode *inode,
struct folio *folio = fbatch.folios[i];
folio_lock(folio);
if (unlikely(folio->mapping != mapping)) {
/* Exclude folios removed from the address space */
folio_unlock(folio);
continue;
}
head = folio_buffers(folio);
if (!head) {
create_empty_buffers(&folio->page, i_blocksize(inode), 0);