2022-10-16 01:40:25

by Dongliang Mu

Subject: [PATCH v2] fs: jfs: fix shift-out-of-bounds in dbAllocAG

From: Dongliang Mu <[email protected]>

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 MAXMAPSIZE - L2MAXAG, thanks for the help of Dave Kleikamp.
Notethat, for maintainance, I reorganzie error handling code of dbMount.

Reported-by: [email protected]
Signed-off-by: Dongliang Mu <[email protected]>
---
v1->2: fix the size of bmp->db_agl2size; revise the correct upper bound
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 6b838d3ae7c2..962c855631cb 100644
--- a/fs/jfs/jfs_dmap.c
+++ b/fs/jfs/jfs_dmap.c
@@ -155,7 +155,7 @@ 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
@@ -170,8 +170,8 @@ 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. */
@@ -181,9 +181,8 @@ 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);
@@ -194,6 +193,11 @@ 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 > MAXMAPSIZE - 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);
@@ -214,6 +218,12 @@ 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

2022-10-17 20:10:21

by Dave Kleikamp

Subject: Re: [PATCH v2] fs: jfs: fix shift-out-of-bounds in dbAllocAG

Looks good. Pushed to jfs-next.

Thanks,
Shaggy

On 10/15/22 8:25PM, Dongliang Mu wrote:
> From: Dongliang Mu <[email protected]>
>
> 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 MAXMAPSIZE - L2MAXAG, thanks for the help of Dave Kleikamp.
> Notethat, for maintainance, I reorganzie error handling code of dbMount.
>
> Reported-by: [email protected]
> Signed-off-by: Dongliang Mu <[email protected]>
> ---
> v1->2: fix the size of bmp->db_agl2size; revise the correct upper bound
> 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 6b838d3ae7c2..962c855631cb 100644
> --- a/fs/jfs/jfs_dmap.c
> +++ b/fs/jfs/jfs_dmap.c
> @@ -155,7 +155,7 @@ 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
> @@ -170,8 +170,8 @@ 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. */
> @@ -181,9 +181,8 @@ 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);
> @@ -194,6 +193,11 @@ 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 > MAXMAPSIZE - 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);
> @@ -214,6 +218,12 @@ int dbMount(struct inode *ipbmap)
> BMAP_LOCK_INIT(bmp);
>
> return (0);
> +
> +err_release_metapage:
> + release_metapage(mp);
> +err_kfree_bmp:
> + kfree(bmp);
> + return err;
> }
>
>