From: "Darrick J. Wong" djwong@kernel.org
mainline-inclusion from mainline-v5.14-rc1 commit 81a448d7b0668ae39c08e6f34a54cc7eafb844f1 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I4KIAO CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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While reviewing the buffer item recovery code, the thought occurred to me: in V5 filesystems we use log sequence number (LSN) tracking to avoid replaying older metadata updates against newer log items. However, we use the magic number of the ondisk buffer to find the LSN of the ondisk metadata, which means that if an attacker can control the layout of the realtime device precisely enough that the start of an rt bitmap block matches the magic and UUID of some other kind of block, they can control the purported LSN of that spoofed block and thereby break log replay.
Since realtime bitmap and summary blocks don't have headers at all, we have no way to tell if a block really should be replayed. The best we can do is replay unconditionally and hope for the best.
Signed-off-by: Darrick J. Wong djwong@kernel.org Reviewed-by: Dave Chinner dchinner@redhat.com Reviewed-by: Carlos Maiolino cmaiolino@redhat.com Signed-off-by: Guo Xuenan guoxuenan@huawei.com Reviewed-by: Lihong Kou koulihong@huawei.com Reviewed-by: Zhang Yi yi.zhang@huawei.com Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com --- fs/xfs/xfs_buf_item_recover.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/fs/xfs/xfs_buf_item_recover.c b/fs/xfs/xfs_buf_item_recover.c index 05fd816edf59..4775485b4062 100644 --- a/fs/xfs/xfs_buf_item_recover.c +++ b/fs/xfs/xfs_buf_item_recover.c @@ -698,7 +698,8 @@ xlog_recover_do_inode_buffer( static xfs_lsn_t xlog_recover_get_buf_lsn( struct xfs_mount *mp, - struct xfs_buf *bp) + struct xfs_buf *bp, + struct xfs_buf_log_format *buf_f) { uint32_t magic32; uint16_t magic16; @@ -706,11 +707,20 @@ xlog_recover_get_buf_lsn( void *blk = bp->b_addr; uuid_t *uuid; xfs_lsn_t lsn = -1; + uint16_t blft;
/* v4 filesystems always recover immediately */ if (!xfs_sb_version_hascrc(&mp->m_sb)) goto recover_immediately;
+ /* + * realtime bitmap and summary file blocks do not have magic numbers or + * UUIDs, so we must recover them immediately. + */ + blft = xfs_blft_from_flags(buf_f); + if (blft == XFS_BLFT_RTBITMAP_BUF || blft == XFS_BLFT_RTSUMMARY_BUF) + goto recover_immediately; + magic32 = be32_to_cpu(*(__be32 *)blk); switch (magic32) { case XFS_ABTB_CRC_MAGIC: @@ -920,7 +930,7 @@ xlog_recover_buf_commit_pass2( * the verifier will be reset to match whatever recover turns that * buffer into. */ - lsn = xlog_recover_get_buf_lsn(mp, bp); + lsn = xlog_recover_get_buf_lsn(mp, bp, buf_f); if (lsn && lsn != -1 && XFS_LSN_CMP(lsn, current_lsn) >= 0) { trace_xfs_log_recover_buf_skip(log, buf_f); xlog_recover_validate_buf_type(mp, bp, buf_f, NULLCOMMITLSN);