On 6/5/23 9:01AM, Siddh Raman Pant wrote:
In jfs_dmap.c at line 381, BLKTODMAP is used to get a logical block
number inside dbFree(). db_l2nbperpage, which is the log2 number of
blocks per page, is passed as an argument to BLKTODMAP which uses it
for shifting.
Syzbot reported a shift out-of-bounds crash because db_l2nbperpage is
too big. This happens because the large value is set without any
validation in dbMount() at line 181.
Thus, make sure that db_l2nbperpage is correct while mounting.
Reported-and-tested-by: syzbot+d2cd27dcf8e04b232eb2@xxxxxxxxxxxxxxxxxxxxxxxxx
Link: https://syzkaller.appspot.com/bug?id=2a70a453331db32ed491f5cbb07e81bf2d225715
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Siddh Raman Pant <code@xxxxxxxx>
---
fs/jfs/jfs_dmap.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/fs/jfs/jfs_dmap.c b/fs/jfs/jfs_dmap.c
index a3eb1e826947..62f058822a3a 100644
--- a/fs/jfs/jfs_dmap.c
+++ b/fs/jfs/jfs_dmap.c
@@ -178,7 +178,13 @@ int dbMount(struct inode *ipbmap)
dbmp_le = (struct dbmap_disk *) mp->data;
bmp->db_mapsize = le64_to_cpu(dbmp_le->dn_mapsize);
bmp->db_nfree = le64_to_cpu(dbmp_le->dn_nfree);
+
bmp->db_l2nbperpage = le32_to_cpu(dbmp_le->dn_l2nbperpage);
+ if (bmp->db_l2nbperpage > L2MAXL0SIZE) {
Actually the sanity check should be much smaller. The maximum value
should be L2PSIZE - log2(MINBLOCKSIZE). In reality, I think it's always
zero.
Shaggy
+ err = -EINVAL;
+ goto err_release_metapage;
+ }
+
bmp->db_numag = le32_to_cpu(dbmp_le->dn_numag);
if (!bmp->db_numag) {
err = -EINVAL;
