The patch titled
Subject: reiserfs: add comment to explain endianness issue in xattr_hash
has been added to the -mm tree. Its filename is
reiserfs-add-comment-to-explain-endianness-issue-in-xattr_hash.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/reiserfs-add-comment-to-explain-endianness-issue-in-xattr_hash.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/reiserfs-add-comment-to-explain-endianness-issue-in-xattr_hash.patch
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------------------------------------------------------
From: Bharath Vedartham <linux.bhar@xxxxxxxxx>
Subject: reiserfs: add comment to explain endianness issue in xattr_hash
csum_partial() gives different results for little-endian and big-endian
hosts. This causes images created on little-endian hosts and mounted on
big endian hosts to see csum mismatches. This causes an endianness bug.
Sparse gives a warning as csum_partial returns a restricted integer type
__wsum_t and xattr_hash expects __u32. This warning acts as a reminder
for this bug and should not be suppressed.
This comment aims to convey these endianness issues.
Link: http://lkml.kernel.org/r/20190423161831.GA15387@bharath12345-Inspiron-5559
Signed-off-by: Bharath Vedartham <linux.bhar@xxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: Jeff Mahoney <jeffm@xxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/reiserfs/xattr.c | 10 ++++++++++
1 file changed, 10 insertions(+)
--- a/fs/reiserfs/xattr.c~reiserfs-add-comment-to-explain-endianness-issue-in-xattr_hash
+++ a/fs/reiserfs/xattr.c
@@ -450,6 +450,16 @@ fail:
static inline __u32 xattr_hash(const char *msg, int len)
{
+ /*
+ * csum_partial() gives different results for little-endian and
+ * big endian hosts. Images created on little-endian hosts and
+ * mounted on big-endian hosts(and vice versa) will see csum mismatches
+ * when trying to fetch xattrs. Treating the hash as __wsum_t would
+ * lower the frequency of mismatch. This is an endianness bug in reiserfs.
+ * The return statement would result in a sparse warning. Do not fix the sparse
+ * warning so as to not hide the reminder of the bug.
+ */
+
return csum_partial(msg, len, 0);
}
_
Patches currently in -mm which might be from linux.bhar@xxxxxxxxx are
reiserfs-add-comment-to-explain-endianness-issue-in-xattr_hash.patch
