Patch "fs: jfs: fix shift-out-of-bounds in dbAllocAG" has been added to the 4.9-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    fs: jfs: fix shift-out-of-bounds in dbAllocAG

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     fs-jfs-fix-shift-out-of-bounds-in-dballocag.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 3155d422ab0e18c154fe8c6f09202638d7585c27
Author: Dongliang Mu <mudongliangabcd@xxxxxxxxx>
Date:   Tue Oct 18 08:48:07 2022 -0500

    fs: jfs: fix shift-out-of-bounds in dbAllocAG
    
    [ Upstream commit 898f706695682b9954f280d95e49fa86ffa55d08 ]
    
    Syzbot found a crash : UBSAN: shift-out-of-bounds in dbAllocAG. The
    underlying bug is the missing check of bmp->db_agl2size. The field can
    be greater than 64 and trigger the shift-out-of-bounds.
    
    Fix this bug by adding a check of bmp->db_agl2size in dbMount since this
    field is used in many following functions. The upper bound for this
    field is L2MAXL2SIZE - L2MAXAG, thanks for the help of Dave Kleikamp.
    Note that, for maintenance, I reorganized error handling code of dbMount.
    
    Reported-by: syzbot+15342c1aa6a00fb7a438@xxxxxxxxxxxxxxxxxxxxxxxxx
    Signed-off-by: Dongliang Mu <mudongliangabcd@xxxxxxxxx>
    Signed-off-by: Dave Kleikamp <dave.kleikamp@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/jfs/jfs_dmap.c b/fs/jfs/jfs_dmap.c
index a07fbb60ac3c..a46fa0f3db57 100644
--- a/fs/jfs/jfs_dmap.c
+++ b/fs/jfs/jfs_dmap.c
@@ -168,7 +168,7 @@ int dbMount(struct inode *ipbmap)
 	struct bmap *bmp;
 	struct dbmap_disk *dbmp_le;
 	struct metapage *mp;
-	int i;
+	int i, err;
 
 	/*
 	 * allocate/initialize the in-memory bmap descriptor
@@ -183,8 +183,8 @@ int dbMount(struct inode *ipbmap)
 			   BMAPBLKNO << JFS_SBI(ipbmap->i_sb)->l2nbperpage,
 			   PSIZE, 0);
 	if (mp == NULL) {
-		kfree(bmp);
-		return -EIO;
+		err = -EIO;
+		goto err_kfree_bmp;
 	}
 
 	/* copy the on-disk bmap descriptor to its in-memory version. */
@@ -194,9 +194,8 @@ int dbMount(struct inode *ipbmap)
 	bmp->db_l2nbperpage = le32_to_cpu(dbmp_le->dn_l2nbperpage);
 	bmp->db_numag = le32_to_cpu(dbmp_le->dn_numag);
 	if (!bmp->db_numag) {
-		release_metapage(mp);
-		kfree(bmp);
-		return -EINVAL;
+		err = -EINVAL;
+		goto err_release_metapage;
 	}
 
 	bmp->db_maxlevel = le32_to_cpu(dbmp_le->dn_maxlevel);
@@ -207,6 +206,11 @@ int dbMount(struct inode *ipbmap)
 	bmp->db_agwidth = le32_to_cpu(dbmp_le->dn_agwidth);
 	bmp->db_agstart = le32_to_cpu(dbmp_le->dn_agstart);
 	bmp->db_agl2size = le32_to_cpu(dbmp_le->dn_agl2size);
+	if (bmp->db_agl2size > L2MAXL2SIZE - L2MAXAG) {
+		err = -EINVAL;
+		goto err_release_metapage;
+	}
+
 	for (i = 0; i < MAXAG; i++)
 		bmp->db_agfree[i] = le64_to_cpu(dbmp_le->dn_agfree[i]);
 	bmp->db_agsize = le64_to_cpu(dbmp_le->dn_agsize);
@@ -227,6 +231,12 @@ int dbMount(struct inode *ipbmap)
 	BMAP_LOCK_INIT(bmp);
 
 	return (0);
+
+err_release_metapage:
+	release_metapage(mp);
+err_kfree_bmp:
+	kfree(bmp);
+	return err;
 }