From: Bharath Vedartham Date: Tue, 14 May 2019 22:44:29 +0000 (-0700) Subject: reiserfs: add comment to explain endianness issue in xattr_hash X-Git-Tag: v5.2-rc1~62^2~55 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=672cdd56f0ae95069e399db790dbf2e303ac72b7;p=linux.git 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. [akpm@linux-foundation.org: coding-style fixes] Link: http://lkml.kernel.org/r/20190423161831.GA15387@bharath12345-Inspiron-5559 Signed-off-by: Bharath Vedartham Cc: Al Viro Cc: Jann Horn Cc: Jeff Mahoney Cc: Jan Kara Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/fs/reiserfs/xattr.c b/fs/reiserfs/xattr.c index 32d8986c26fb..b5b26d8a192c 100644 --- a/fs/reiserfs/xattr.c +++ b/fs/reiserfs/xattr.c @@ -450,6 +450,15 @@ 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 a reminder of the bug. + */ return csum_partial(msg, len, 0); }