Messages in this thread Patch in this message | | | Date | Tue, 23 Apr 2019 21:48:31 +0530 | From | Bharath Vedartham <> | Subject | [PATCH] reiserfs: Add comment to explain endianness issue in xattr_hash |
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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.
Signed-off-by: Bharath Vedartham <linux.bhar@gmail.com> --- fs/reiserfs/xattr.c | 10 ++++++++++ 1 file changed, 10 insertions(+)
diff --git a/fs/reiserfs/xattr.c b/fs/reiserfs/xattr.c index 32d8986..0ea6654 100644 --- a/fs/reiserfs/xattr.c +++ b/fs/reiserfs/xattr.c @@ -450,6 +450,16 @@ static struct page *reiserfs_get_page(struct inode *dir, size_t n) 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); } -- 2.7.4
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