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Subject[PATCH AUTOSEL 4.14 1/8] fs: jfs: fix shift-out-of-bounds in dbAllocAG
Date
From: Dongliang Mu <mudongliangabcd@gmail.com>

[ 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@syzkaller.appspotmail.com
Signed-off-by: Dongliang Mu <mudongliangabcd@gmail.com>
Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/jfs/jfs_dmap.c | 22 ++++++++++++++++------
1 file changed, 16 insertions(+), 6 deletions(-)

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;
}


--
2.35.1
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