linux-kernel - [PATCH] jfs: Fix shift-out-of-bounds in jfs

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Date:   Wed, 16 Nov 2022 09:36:00 +0800
From:   Liao Chang <liaochang1@...wei.com>
To:     <shaggy@...nel.org>
CC:     <jfs-discussion@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>, <liaochang1@...wei.com>
Subject: [PATCH] jfs: Fix  shift-out-of-bounds in jfs_statfs

Syzkaller report issue as follows:

UBSAN: shift-out-of-bounds in fs/jfs/super.c:140:14
shift exponent -236023038 is negative
CPU: 0 PID: 3985 Comm: syz-executor.4 Not tainted 6.1.0-rc2-syzkaller #0
Hardware name: Google Compute Engine, BIOS Google 10/11/2022
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88
 dump_stack_lvl+0x1b1/0x28e lib/dump_stack.c:106
 ubsan_epilogue lib/ubsan.c:151
 __ubsan_handle_shift_out_of_bounds+0x33d/0x3b0 lib/ubsan.c:322
 jfs_statfs+0x503/0x510 fs/jfs/super.c:140
 statfs_by_dentry fs/statfs.c:66
 vfs_statfs+0x136/0x310 fs/statfs.c:90
 user_statfs fs/statfs.c:105
__ubsan_handle_shift_out_of_bounds __do_sys_statfs fs/statfs.c:195
 __se_sys_statfs fs/statfs.c:192
 __x64_sys_statfs+0x120/0x230 fs/statfs.c:192
 do_syscall_x64 arch/x86/entry/common.c:50
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
 </TASK>

The on-disk inode map control structure contains a number indicates the
log2 number of blocks per inode extent, which will be used as the shift
to calculate the number of free blocks in jfs_statfs, so it needs to
ensure the on-disk log2 number is positive and less than 64 on JFS
mount.

Reported-by: syzbot+3424c9550a49659f1704@...kaller.appspotmail.com
Signed-off-by: Liao Chang <liaochang1@...wei.com>
---
 fs/jfs/jfs_imap.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/jfs/jfs_imap.c b/fs/jfs/jfs_imap.c
index 799d3837e7c2..1ff632c55acf 100644
--- a/fs/jfs/jfs_imap.c
+++ b/fs/jfs/jfs_imap.c
@@ -124,6 +124,12 @@ int diMount(struct inode *ipimap)
 	atomic_set(&imap->im_numfree, le32_to_cpu(dinom_le->in_numfree));
 	imap->im_nbperiext = le32_to_cpu(dinom_le->in_nbperiext);
 	imap->im_l2nbperiext = le32_to_cpu(dinom_le->in_l2nbperiext);
+	if (imap->im_l2nbperiext < 0 ||
+	    imap->im_l2nbperiext >= sizeof(s64) * 8) {
+		kfree(imap);
+		return -EINVAL;
+	}
+
 	for (index = 0; index < MAXAG; index++) {
 		imap->im_agctl[index].inofree =
 		    le32_to_cpu(dinom_le->in_agctl[index].inofree);
-- 
2.17.1