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xfs: catch invalid negative blknos in _xfs_buf_find()

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Here blkno is a daddr_t, which is a __s64; it's possible to hold
a value which is negative, and thus pass the (blkno >= eofs)
test.  Then we try to do a xfs_perag_get() for a ridiculous
agno via xfs_daddr_to_agno(), and bad things happen when that
fails, and returns a null pag which is dereferenced shortly
thereafter.

Found via a user-supplied fuzzed image...

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
This commit is contained in:
Eric Sandeen 2014-11-28 14:03:55 +11:00 committed by Dave Chinner
parent 91ee575f2b
commit db52d09ecb
1 changed files with 1 additions and 1 deletions
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2
fs/xfs/xfs_buf.c
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@ -461,7 +461,7 @@ _xfs_buf_find(
* have to check that the buffer falls within the filesystem bounds.
*/
eofs = XFS_FSB_TO_BB(btp->bt_mount, btp->bt_mount->m_sb.sb_dblocks);
if (blkno >= eofs) {
if (blkno < 0 || blkno >= eofs) {
/*
* XXX (dgc): we should really be returning -EFSCORRUPTED here,
* but none of the higher level infrastructure supports