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jfs: Fix shift-out-of-bounds in dbDiscardAG

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When searching for the next smaller log2 block, BLKSTOL2() returned 0,
causing shift exponent -1 to be negative.

This patch fixes the issue by exiting the loop directly when negative
shift is found.

Reported-by: syzbot+61be3359d2ee3467e7e4@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=61be3359d2ee3467e7e4
Signed-off-by: Pei Li <peili.dev@gmail.com>
Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
This commit is contained in:
Pei Li 2024-06-25 09:42:05 -07:00 committed by Dave Kleikamp
parent f73f969b2e
commit 7063b80268
1 changed files with 2 additions and 0 deletions
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2
fs/jfs/jfs_dmap.c
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@ -1626,6 +1626,8 @@ s64 dbDiscardAG(struct inode *ip, int agno, s64 minlen)
} else if (rc == -ENOSPC) { } else if (rc == -ENOSPC) {
/* search for next smaller log2 block */ /* search for next smaller log2 block */
l2nb = BLKSTOL2(nblocks) - 1; l2nb = BLKSTOL2(nblocks) - 1;
if (unlikely(l2nb < 0))
break;
nblocks = 1LL << l2nb; nblocks = 1LL << l2nb;
} else { } else {
/* Trim any already allocated blocks */ /* Trim any already allocated blocks */