linux-kernel - [PATCH 3.12 084/123] xfs: fix remote symlinks on V5/CRC filesystems

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Message-Id: <95a57b3f679f946cef4a8fbca1bd7a36a364dda5.1438699154.git.jslaby@suse.cz>
Date:	Tue,  4 Aug 2015 16:40:28 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Eric Sandeen <sandeen@...hat.com>,
	Dave Chinner <david@...morbit.com>, Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 084/123] xfs: fix remote symlinks on V5/CRC filesystems

From: Eric Sandeen <sandeen@...hat.com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit 2ac56d3d4bd625450a54d4c3f9292d58f6b88232 upstream.

If we create a CRC filesystem, mount it, and create a symlink with
a path long enough that it can't live in the inode, we get a very
strange result upon remount:

# ls -l mnt
total 4
lrwxrwxrwx. 1 root root 929 Jun 15 16:58 link -> XSLM

XSLM is the V5 symlink block header magic (which happens to be
followed by a NUL, so the string looks terminated).

xfs_readlink_bmap() advanced cur_chunk by the size of the header
for CRC filesystems, but never actually used that pointer; it
kept reading from bp->b_addr, which is the start of the block,
rather than the start of the symlink data after the header.

Looks like this problem goes back to v3.10.

Fixing this gets us reading the proper link target, again.

Signed-off-by: Eric Sandeen <sandeen@...hat.com>
Reviewed-by: Dave Chinner <dchinner@...hat.com>
Signed-off-by: Dave Chinner <david@...morbit.com>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 fs/xfs/xfs_symlink.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/xfs/xfs_symlink.c b/fs/xfs/xfs_symlink.c
index f622a97a7e33..117a149ee4a7 100644
--- a/fs/xfs/xfs_symlink.c
+++ b/fs/xfs/xfs_symlink.c
@@ -102,7 +102,7 @@ xfs_readlink_bmap(
 			cur_chunk += sizeof(struct xfs_dsymlink_hdr);
 		}
 
-		memcpy(link + offset, bp->b_addr, byte_cnt);
+		memcpy(link + offset, cur_chunk, byte_cnt);
 
 		pathlen -= byte_cnt;
 		offset += byte_cnt;
-- 
2.5.0

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