[3.19.y-ckt stable] Patch "xfs: fix remote symlinks on V5/CRC filesystems" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    xfs: fix remote symlinks on V5/CRC filesystems

to the linux-3.19.y-queue branch of the 3.19.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.19.y-queue

This patch is scheduled to be released in version 3.19.y-ckt4.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.19.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 065bac50bb23bd9e9e15f6476bbded6cd068e07b Mon Sep 17 00:00:00 2001
From: Eric Sandeen <sandeen at redhat.com>
Date: Mon, 22 Jun 2015 09:42:48 +1000
Subject: xfs: fix remote symlinks on V5/CRC filesystems

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 at redhat.com>
Reviewed-by: Dave Chinner <dchinner at redhat.com>
Signed-off-by: Dave Chinner <david at fromorbit.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 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 25791df..e0b50ed 100644
--- a/fs/xfs/xfs_symlink.c
+++ b/fs/xfs/xfs_symlink.c
@@ -104,7 +104,7 @@ 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;
--
1.9.1