[PATCH V2] jfs: Initialized first 8 members of the dinomap when creating imap

[Edward Adam Davis]

syzbot reported a uninit-value in diFree. [1]

When print_hex_dump() is called to print the first 32 bytes of imap, the
first 8 members in struct dinomap are the first 32 bytes of imap, because
in_numinos, in_numfree, in_diskblock and in_maxag are not initialized when
imap is created.

When creating imap, set in_numinos, in_numfree, in_diskblock and in_maxag
to 0 to prevent this issue from happening.

[1]
BUG: KMSAN: uninit-value in hex_dump_to_buffer+0x888/0x1100 lib/hexdump.c:171
 hex_dump_to_buffer+0x888/0x1100 lib/hexdump.c:171
 print_hex_dump+0x13d/0x3e0 lib/hexdump.c:276
 diFree+0x5ba/0x4350 fs/jfs/jfs_imap.c:876
 jfs_evict_inode+0x510/0x550 fs/jfs/inode.c:156
 evict+0x723/0xd10 fs/inode.c:796
 iput_final fs/inode.c:1946 [inline]
 iput+0x97b/0xdb0 fs/inode.c:1972
 txUpdateMap+0xf3e/0x1150 fs/jfs/jfs_txnmgr.c:2367
 txLazyCommit fs/jfs/jfs_txnmgr.c:2664 [inline]
 jfs_lazycommit+0x627/0x11d0 fs/jfs/jfs_txnmgr.c:2733
 kthread+0x6b9/0xef0 kernel/kthread.c:464
 ret_from_fork+0x6d/0x90 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Uninit was created at:
 slab_post_alloc_hook mm/slub.c:4121 [inline]
 slab_alloc_node mm/slub.c:4164 [inline]
 __kmalloc_cache_noprof+0x8e3/0xdf0 mm/slub.c:4320
 kmalloc_noprof include/linux/slab.h:901 [inline]
 diMount+0x61/0x7f0 fs/jfs/jfs_imap.c:105
 jfs_mount+0xa8e/0x11d0 fs/jfs/jfs_mount.c:176
 jfs_fill_super+0xa47/0x17c0 fs/jfs/super.c:523
 get_tree_bdev_flags+0x6ec/0x910 fs/super.c:1636
 get_tree_bdev+0x37/0x50 fs/super.c:1659
 jfs_get_tree+0x34/0x40 fs/jfs/super.c:635
 vfs_get_tree+0xb1/0x5a0 fs/super.c:1814
 do_new_mount+0x71f/0x15e0 fs/namespace.c:3560
 path_mount+0x742/0x1f10 fs/namespace.c:3887
 do_mount fs/namespace.c:3900 [inline]
 __do_sys_mount fs/namespace.c:4111 [inline]
 __se_sys_mount+0x71f/0x800 fs/namespace.c:4088
 __x64_sys_mount+0xe4/0x150 fs/namespace.c:4088
 x64_sys_call+0x39bf/0x3c30 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83

Reported-by: syzbot+df6cdcb35904203d2b6d@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=df6cdcb35904203d2b6d
Tested-by: syzbot+df6cdcb35904203d2b6d@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Edward Adam Davis <eadavis@xxxxxx>
---
V1 -> V2: add missing others two fields of dinomap

 fs/jfs/jfs_imap.c | 4 ++++
 fs/jfs/jfs_imap.h | 2 ++
 2 files changed, 6 insertions(+)

diff --git a/fs/jfs/jfs_imap.c b/fs/jfs/jfs_imap.c
index a360b24ed320..0cedaccb7218 100644
--- a/fs/jfs/jfs_imap.c
+++ b/fs/jfs/jfs_imap.c
@@ -134,6 +134,10 @@ int diMount(struct inode *ipimap)
 		imap->im_agctl[index].numfree =
 		    le32_to_cpu(dinom_le->in_agctl[index].numfree);
 	}
+	imap->im_diskblock = 0;
+	imap->im_maxag = 0;
+	imap->im_enuminos = 0;
+	imap->im_enumfree = 0;
 
 	/* release the buffer. */
 	release_metapage(mp);
diff --git a/fs/jfs/jfs_imap.h b/fs/jfs/jfs_imap.h
index dd7409febe28..9af1da2e4591 100644
--- a/fs/jfs/jfs_imap.h
+++ b/fs/jfs/jfs_imap.h
@@ -144,6 +144,8 @@ struct inomap {
  */
 #define	im_diskblock	im_imap.in_diskblock
 #define	im_maxag	im_imap.in_maxag
+#define	im_enuminos	im_imap.in_numinos
+#define	im_enumfree	im_imap.in_numfree
 
 extern int diFree(struct inode *);
 extern int diAlloc(struct inode *, bool, struct inode *);
-- 
2.43.0