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filemap: Fix bounds checking in filemap_read()

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If the caller supplies an iocb->ki_pos value that is close to the
filesystem upper limit, and an iterator with a count that causes us to
overflow that limit, then filemap_read() enters an infinite loop.

This behaviour was discovered when testing xfstests generic/525 with the
"localio" optimisation for loopback NFS mounts.

Reported-by: Mike Snitzer <snitzer@kernel.org>
Fixes: c2a9737f45 ("vfs,mm: fix a dead loop in truncate_inode_pages_range()")
Tested-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Trond Myklebust 2024-09-13 13:57:04 -04:00 committed by Linus Torvalds
parent a9cda7c0ff
commit ace149e083
1 changed files with 1 additions and 1 deletions
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2
mm/filemap.c
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@ -2625,7 +2625,7 @@ ssize_t filemap_read(struct kiocb *iocb, struct iov_iter *iter,
if (unlikely(!iov_iter_count(iter))) if (unlikely(!iov_iter_count(iter)))
return 0; return 0;
iov_iter_truncate(iter, inode->i_sb->s_maxbytes); iov_iter_truncate(iter, inode->i_sb->s_maxbytes - iocb->ki_pos);
folio_batch_init(&fbatch); folio_batch_init(&fbatch);
do { do {