From 342b52596ce27f30b59622b67da188c4a3adbeee Mon Sep 17 00:00:00 2001
From: Wu Guanghao <wuguanghao3@huawei.com>
Date: Wed, 21 Jun 2023 09:25:27 +0000
Subject: [PATCH] mkfs.xfs: fix segmentation fault caused by accessing a null
 pointer

We encountered a segfault while testing the mkfs.xfs + iscsi.

(gdb) bt
#0 libxfs_log_sb (tp=0xaaaafaea0630) at xfs_sb.c:810
#1 0x0000aaaaca991468 in __xfs_trans_commit (tp=<optimized out>, tp@entry=0xaaaafaea0630, regrant=regrant@entry=true) at trans.c:995
#2 0x0000aaaaca991790 in libxfs_trans_roll (tpp=tpp@entry=0xfffffe1f3018) at trans.c:103
#3 0x0000aaaaca9bcde8 in xfs_dialloc_roll (agibp=0xaaaafaea2fa0, tpp=0xfffffe1f31c8) at xfs_ialloc.c:1561
#4 xfs_dialloc_try_ag (ok_alloc=true, new_ino=<synthetic pointer>, parent=0, pag=0xaaaafaea0210, tpp=0xfffffe1f31c8) at xfs_ialloc.c:1698
#5 xfs_dialloc (tpp=tpp@entry=0xfffffe1f31c8, parent=0, mode=mode@entry=16877, new_ino=new_ino@entry=0xfffffe1f3128) at xfs_ialloc.c:1776
#6 0x0000aaaaca9925b0 in libxfs_dir_ialloc (tpp=tpp@entry=0xfffffe1f31c8, dp=dp@entry=0x0, mode=mode@entry=16877, nlink=nlink@entry=1, rdev=rdev@entry=0, cr=cr@entry=0xfffffe1f31d0,
	fsx=fsx@entry=0xfffffe1f36a4, ipp=ipp@entry=0xfffffe1f31c0) at util.c:525
#7 0x0000aaaaca988fac in parseproto (mp=0xfffffe1f36c8, pip=0x0, fsxp=0xfffffe1f36a4, pp=0xfffffe1f3370, name=0x0) at proto.c:552
#8 0x0000aaaaca9867a4 in main (argc=<optimized out>, argv=<optimized out>) at xfs_mkfs.c:4217

(gdb) p bp
$1 = 0x0

```
void
xfs_log_sb(
        struct xfs_trans        *tp)
{
        // iscsi offline
        ...
        // failed to read sb, bp = NULL
        struct xfs_buf          *bp = xfs_trans_getsb(tp);
        ...
}
```

When writing data to sb, if the device is abnormal at this time,
the bp may be empty. Using it without checking will result in
a segfault.

So before using it, we need to check if the bp is empty and return
the error.

Signed-off-by: Wu Guanghao <wuguanghao3@huawei.com>
---
 libxfs/trans.c         |  4 +++-
 libxfs/xfs_attr_leaf.c |  2 +-
 libxfs/xfs_bmap.c      |  8 ++++++--
 libxfs/xfs_sb.c        | 25 ++++++++++++++++++++++---
 libxfs/xfs_sb.h        |  2 +-
 mkfs/proto.c           | 15 ++++++++++++---
 6 files changed, 45 insertions(+), 11 deletions(-)

diff --git a/libxfs/trans.c b/libxfs/trans.c
index fd2e6f9..a43472f 100644
--- a/libxfs/trans.c
+++ b/libxfs/trans.c
@@ -975,7 +975,9 @@ __xfs_trans_commit(
 			sbp->sb_fdblocks += tp->t_fdblocks_delta;
 		if (tp->t_frextents_delta)
 			sbp->sb_frextents += tp->t_frextents_delta;
-		xfs_log_sb(tp);
+		error = xfs_log_sb(tp);
+		if (error)
+		        goto out_unreserve;
 	}
 
 	trans_committed(tp);
diff --git a/libxfs/xfs_attr_leaf.c b/libxfs/xfs_attr_leaf.c
index cfb6bf1..9522155 100644
--- a/libxfs/xfs_attr_leaf.c
+++ b/libxfs/xfs_attr_leaf.c
@@ -629,7 +629,7 @@ xfs_sbversion_add_attr2(xfs_mount_t *mp, xfs_trans_t *tp)
 		if (!xfs_sb_version_hasattr2(&mp->m_sb)) {
 			xfs_sb_version_addattr2(&mp->m_sb);
 			spin_unlock(&mp->m_sb_lock);
-			xfs_log_sb(tp);
+			ASSERT(!xfs_log_sb(tp));
 		} else
 			spin_unlock(&mp->m_sb_lock);
 	}
diff --git a/libxfs/xfs_bmap.c b/libxfs/xfs_bmap.c
index a548507..16dbe71 100644
--- a/libxfs/xfs_bmap.c
+++ b/libxfs/xfs_bmap.c
@@ -1122,8 +1122,12 @@ xfs_bmap_add_attrfork(
 			log_sb = true;
 		}
 		spin_unlock(&mp->m_sb_lock);
-		if (log_sb)
-			xfs_log_sb(tp);
+		if (log_sb) {
+			error = xfs_log_sb(tp);
+			if (error)
+				goto trans_cancel;
+		}
+
 	}
 
 	error = xfs_trans_commit(tp);
diff --git a/libxfs/xfs_sb.c b/libxfs/xfs_sb.c
index b2e214e..df7aec5 100644
--- a/libxfs/xfs_sb.c
+++ b/libxfs/xfs_sb.c
@@ -784,13 +784,16 @@ xfs_sb_mount_common(
  * level of locking that is needed to protect the in-core superblock from
  * concurrent access.
  */
-void
+int
 xfs_log_sb(
 	struct xfs_trans	*tp)
 {
 	struct xfs_mount	*mp = tp->t_mountp;
 	struct xfs_buf		*bp = xfs_trans_getsb(tp);
 
+	if (!bp)
+		return -EIO;
+
 	/*
 	 * Lazy sb counters don't update the in-core superblock so do that now.
 	 * If this is at unmount, the counters will be exactly correct, but at
@@ -808,6 +811,8 @@ xfs_log_sb(
 	xfs_sb_to_disk(bp->b_addr, &mp->m_sb);
 	xfs_trans_buf_set_type(tp, bp, XFS_BLFT_SB_BUF);
 	xfs_trans_log_buf(tp, bp, 0, sizeof(struct xfs_dsb) - 1);
+
+	return 0;
 }
 
 /*
@@ -834,7 +839,13 @@ xfs_sync_sb(
 	if (error)
 		return error;
 
-	xfs_log_sb(tp);
+	error = xfs_log_sb(tp);
+	if (error) {
+		xfs_trans_cancel(tp);
+		return error;
+	}
+
+
 	if (wait)
 		xfs_trans_set_sync(tp);
 	return xfs_trans_commit(tp);
@@ -931,7 +942,15 @@ xfs_sync_sb_buf(
 		return error;
 
 	bp = xfs_trans_getsb(tp);
-	xfs_log_sb(tp);
+	if (!bp) {
+	        xfs_trans_cancel(tp);
+	        return -EIO;
+	}
+	error = xfs_log_sb(tp);
+	if (error) {
+	        xfs_trans_cancel(tp);
+	        return error;
+	}
 	xfs_trans_bhold(tp, bp);
 	xfs_trans_set_sync(tp);
 	error = xfs_trans_commit(tp);
diff --git a/libxfs/xfs_sb.h b/libxfs/xfs_sb.h
index 0c1602d..33ca6bb 100644
--- a/libxfs/xfs_sb.h
+++ b/libxfs/xfs_sb.h
@@ -13,7 +13,7 @@ struct xfs_trans;
 struct xfs_fsop_geom;
 struct xfs_perag;
 
-extern void	xfs_log_sb(struct xfs_trans *tp);
+extern int	xfs_log_sb(struct xfs_trans *tp);
 extern int	xfs_sync_sb(struct xfs_mount *mp, bool wait);
 extern int	xfs_sync_sb_buf(struct xfs_mount *mp);
 extern void	xfs_sb_mount_common(struct xfs_mount *mp, struct xfs_sb *sbp);
diff --git a/mkfs/proto.c b/mkfs/proto.c
index ef130ed..005b6e3 100644
--- a/mkfs/proto.c
+++ b/mkfs/proto.c
@@ -557,7 +557,10 @@ parseproto(
 		if (!pip) {
 			pip = ip;
 			mp->m_sb.sb_rootino = ip->i_ino;
-			libxfs_log_sb(tp);
+			error = -libxfs_log_sb(tp);
+			if (error) {
+			        fail(_("Log sb failed"), error);
+			}
 			isroot = 1;
 		} else {
 			libxfs_trans_ijoin(tp, pip, 0);
@@ -656,7 +659,10 @@ rtinit(
 	rbmip->i_diflags = XFS_DIFLAG_NEWRTBM;
 	*(uint64_t *)&VFS_I(rbmip)->i_atime = 0;
 	libxfs_trans_log_inode(tp, rbmip, XFS_ILOG_CORE);
-	libxfs_log_sb(tp);
+	error = -libxfs_log_sb(tp);
+	if (error) {
+	        fail(_("Log sb failed"), error);
+	}
 	mp->m_rbmip = rbmip;
 	error = -libxfs_dir_ialloc(&tp, NULL, S_IFREG, 1, 0,
 					&creds, &fsxattrs, &rsumip);
@@ -666,7 +672,10 @@ rtinit(
 	mp->m_sb.sb_rsumino = rsumip->i_ino;
 	rsumip->i_disk_size = mp->m_rsumsize;
 	libxfs_trans_log_inode(tp, rsumip, XFS_ILOG_CORE);
-	libxfs_log_sb(tp);
+	error = -libxfs_log_sb(tp);
+	if (error) {
+	        fail(_("Log sb failed"), error);
+	}
 	error = -libxfs_trans_commit(tp);
 	if (error)
 		fail(_("Completion of the realtime summary inode failed"),
-- 
2.33.0

