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jfs: jfs_dmap: Validate db_l2nbperpage while mounting 

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.

Max number of blocks per page = Page size / Min block size
=> log2(Max num_block per page) = log2(Page size / Min block size)
				= log2(Page size) - log2(Min block size)

=> Max db_l2nbperpage = L2PSIZE - L2MINBLOCKSIZE

Reported-and-tested-by: syzbot+d2cd27dcf8e04b232eb2@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?id=2a70a453331db32ed491f5cbb07e81bf2d225715
Cc: stable@vger.kernel.org
Suggested-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Signed-off-by: Siddh Raman Pant <code@siddh.me>
Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
This commit is contained in:
Siddh Raman Pant 2023-06-20 22:17:00 +05:30 committed by Dave Kleikamp
parent 692b7dc87c
commit 11509910c5
2 changed files with 8 additions and 0 deletions
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6
fs/jfs/jfs_dmap.c
View File

@ -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 > L2PSIZE - L2MINBLOCKSIZE) {
err = -EINVAL;
goto err_release_metapage;
}
bmp->db_numag = le32_to_cpu(dbmp_le->dn_numag);
if (!bmp->db_numag) {
err = -EINVAL;

2
fs/jfs/jfs_filsys.h
View File

@ -122,7 +122,9 @@
#define NUM_INODE_PER_IAG INOSPERIAG
#define MINBLOCKSIZE 512
#define L2MINBLOCKSIZE 9
#define MAXBLOCKSIZE 4096
#define L2MAXBLOCKSIZE 12
#define MAXFILESIZE ((s64)1 << 52)
#define JFS_LINK_MAX 0xffffffff