xfs: validate log record version against superblock log version

Syzbot creates a fuzzed record where xfs_has_logv2() but the
xlog_rec_header h_version != XLOG_VERSION_2. This causes a
KASAN: slab-out-of-bounds read in xlog_do_recovery_pass() ->
xlog_recover_process() -> xlog_cksum().

Fix by adding a check to xlog_valid_rec_header() to abort journal
recovery if the xlog_rec_header h_version does not match the super
block log version.

A file system with a version 2 log will only ever set
XLOG_VERSION_2 in its headers (and v1 will only ever set V_1), so if
there is any mismatch, either the journal or the superblock has been
corrupted and therefore we abort processing with a -EFSCORRUPTED error
immediately.

Also, refactor the structure of the validity checks for better
readability. At the default error level (LOW), XFS_IS_CORRUPT() emits
the condition that failed, the file and line number it is
located at, then dumps the stack. This gives us everything we need
to know about the failure if we do a single validity check per
XFS_IS_CORRUPT().

Reported-by: syzbot+9f6d080dece587cfdd4c@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=9f6d080dece587cfdd4c
Tested-by: syzbot+9f6d080dece587cfdd4c@syzkaller.appspotmail.com
Fixes: 45cf976008dd ("xfs: fix log recovery buffer allocation for the legacy h_size fixup")
Signed-off-by: Raphael Pinsonneault-Thibeault <rpthibeault@gmail.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Carlos Maiolino <cem@kernel.org>

diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index 94e8598056eb88c594b1fab131d0a082b3a5c4b0..935905743f942fe2021f852359c19646fb706ceb 100644 (file)
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -2953,18 +2953,23 @@ xlog_valid_rec_header(
        xfs_daddr_t             blkno,
        int                     bufsize)
 {
+       struct xfs_mount        *mp = log->l_mp;
+       u32                     h_version = be32_to_cpu(rhead->h_version);
        int                     hlen;
 
-       if (XFS_IS_CORRUPT(log->l_mp,
+       if (XFS_IS_CORRUPT(mp,
                           rhead->h_magicno != cpu_to_be32(XLOG_HEADER_MAGIC_NUM)))
                return -EFSCORRUPTED;
-       if (XFS_IS_CORRUPT(log->l_mp,
-                          (!rhead->h_version ||
-                          (be32_to_cpu(rhead->h_version) &
-                           (~XLOG_VERSION_OKBITS))))) {
-               xfs_warn(log->l_mp, "%s: unrecognised log version (%d).",
-                       __func__, be32_to_cpu(rhead->h_version));
-               return -EFSCORRUPTED;
+
+       /*
+        * The log version must match the superblock
+        */
+       if (xfs_has_logv2(mp)) {
+               if (XFS_IS_CORRUPT(mp, h_version != XLOG_VERSION_2))
+                       return -EFSCORRUPTED;
+       } else {
+               if (XFS_IS_CORRUPT(mp, h_version != XLOG_VERSION_1))
+                       return -EFSCORRUPTED;
        }
 
        /*
@@ -2972,12 +2977,12 @@ xlog_valid_rec_header(
         * and h_len must not be greater than LR buffer size.
         */
        hlen = be32_to_cpu(rhead->h_len);
-       if (XFS_IS_CORRUPT(log->l_mp, hlen <= 0 || hlen > bufsize))
+       if (XFS_IS_CORRUPT(mp, hlen <= 0 || hlen > bufsize))
                return -EFSCORRUPTED;
 
-       if (XFS_IS_CORRUPT(log->l_mp,
-                          blkno > log->l_logBBsize || blkno > INT_MAX))
+       if (XFS_IS_CORRUPT(mp, blkno > log->l_logBBsize || blkno > INT_MAX))
                return -EFSCORRUPTED;
+
        return 0;
 }