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From:   Peng Zhang <zhangpeng362@huawei.com>
To:     <jack@suse.com>, <jack@suse.cz>, <yi.zhang@huawei.com>,
        <yujie.liu@intel.com>, <hch@lst.de>, <akpm@linux-foundation.org>,
        <bvanassche@acm.org>, <willy@infradead.org>
CC:     <linux-kernel@vger.kernel.org>,
        ZhangPeng <zhangpeng362@huawei.com>,
        <syzbot+908340a8367281960537@syzkaller.appspotmail.com>
Subject: [PATCH] udf: Fix a slab-out-of-bounds write bug in udf_write_aext()
Date:   Thu, 10 Nov 2022 01:40:52 +0000
Message-ID: <20221110014052.3039100-1-zhangpeng362@huawei.com>
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From: ZhangPeng <zhangpeng362@huawei.com>

Syzbot reported a slab-out-of-bounds write bug:

loop0: detected capacity change from 0 to 2048
==================================================================
BUG: KASAN: slab-out-of-bounds in udf_write_aext+0x8bc/0x8f0
fs/udf/inode.c:2103
Write of size 4 at addr ffff8880777c63f8 by task syz-executor216/3611

CPU: 0 PID: 3611 Comm: syz-executor216 Not tainted
6.0.0-syzkaller-09589-g55be6084c8e0 #0
Hardware name: Google Compute Engine/Google Compute Engine, BIOS
Google 09/22/2022
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:317 [inline]
 print_report.cold+0x2ba/0x719 mm/kasan/report.c:433
 kasan_report+0xb1/0x1e0 mm/kasan/report.c:495
 udf_write_aext+0x8bc/0x8f0 fs/udf/inode.c:2103
 udf_add_entry+0xd03/0x2ac0 fs/udf/namei.c:482
 udf_mkdir+0x145/0x650 fs/udf/namei.c:681
 vfs_mkdir+0x489/0x740 fs/namei.c:4013
 do_mkdirat+0x28c/0x310 fs/namei.c:4038
 __do_sys_mkdir fs/namei.c:4058 [inline]
 __se_sys_mkdir fs/namei.c:4056 [inline]
 __x64_sys_mkdir+0xf2/0x140 fs/namei.c:4056
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7fef3beda479
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89
f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01
f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe952d4e28 EFLAGS: 00000246 ORIG_RAX: 0000000000000053
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fef3beda479
RDX: 00007fef3be986e3 RSI: 0000000000000000 RDI: 0000000020000000
RBP: 00007fef3be999b0 R08: 00007ffe952d4d10 R09: 0000000000000000
R10: 00007ffe952d4cf0 R11: 0000000000000246 R12: 00007fef3be99a40
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 </TASK>

Allocated by task 3611:
 kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
 kasan_set_track mm/kasan/common.c:45 [inline]
 set_alloc_info mm/kasan/common.c:437 [inline]
 ____kasan_kmalloc mm/kasan/common.c:516 [inline]
 ____kasan_kmalloc mm/kasan/common.c:475 [inline]
 __kasan_kmalloc+0xa9/0xd0 mm/kasan/common.c:525
 kmalloc include/linux/slab.h:600 [inline]
 kmalloc_array include/linux/slab.h:639 [inline]
 kcalloc include/linux/slab.h:671 [inline]
 udf_process_sequence+0xe9/0x4470 fs/udf/super.c:1689
 udf_load_sequence fs/udf/super.c:1813 [inline]
 udf_check_anchor_block+0x44b/0x640 fs/udf/super.c:1852
 udf_scan_anchors+0x1b3/0x6d0 fs/udf/super.c:1885
 udf_find_anchor fs/udf/super.c:1941 [inline]
 udf_load_vrs+0x27b/0xbe0 fs/udf/super.c:2006
 udf_fill_super+0x859/0x1a40 fs/udf/super.c:2184
 mount_bdev+0x34d/0x410 fs/super.c:1400
 legacy_get_tree+0x105/0x220 fs/fs_context.c:610
 vfs_get_tree+0x89/0x2f0 fs/super.c:1530
 do_new_mount fs/namespace.c:3040 [inline]
 path_mount+0x1326/0x1e20 fs/namespace.c:3370
 do_mount fs/namespace.c:3383 [inline]
 __do_sys_mount fs/namespace.c:3591 [inline]
 __se_sys_mount fs/namespace.c:3568 [inline]
 __x64_sys_mount+0x27f/0x300 fs/namespace.c:3568
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Freed by task 3611:
 kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
 kasan_set_track+0x21/0x30 mm/kasan/common.c:45
 kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:370
 ____kasan_slab_free mm/kasan/common.c:367 [inline]
 ____kasan_slab_free+0x166/0x1c0 mm/kasan/common.c:329
 kasan_slab_free include/linux/kasan.h:200 [inline]
 slab_free_hook mm/slub.c:1759 [inline]
 slab_free_freelist_hook+0x8b/0x1c0 mm/slub.c:1785
 slab_free mm/slub.c:3539 [inline]
 kfree+0xe2/0x580 mm/slub.c:4567
 udf_process_sequence+0x421/0x4470 fs/udf/super.c:1781
 udf_load_sequence fs/udf/super.c:1813 [inline]
 udf_check_anchor_block+0x44b/0x640 fs/udf/super.c:1852
 udf_scan_anchors+0x1b3/0x6d0 fs/udf/super.c:1885
 udf_find_anchor fs/udf/super.c:1941 [inline]
 udf_load_vrs+0x27b/0xbe0 fs/udf/super.c:2006
 udf_fill_super+0x859/0x1a40 fs/udf/super.c:2184
 mount_bdev+0x34d/0x410 fs/super.c:1400
 legacy_get_tree+0x105/0x220 fs/fs_context.c:610
 vfs_get_tree+0x89/0x2f0 fs/super.c:1530
 do_new_mount fs/namespace.c:3040 [inline]
 path_mount+0x1326/0x1e20 fs/namespace.c:3370
 do_mount fs/namespace.c:3383 [inline]
 __do_sys_mount fs/namespace.c:3591 [inline]
 __se_sys_mount fs/namespace.c:3568 [inline]
 __x64_sys_mount+0x27f/0x300 fs/namespace.c:3568
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

The buggy address belongs to the object at ffff8880777c6000
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 504 bytes to the right of
 512-byte region [ffff8880777c6000, ffff8880777c6200)

The buggy address belongs to the physical page:
page:ffffea0001ddf100 refcount:1 mapcount:0 mapping:0000000000000000
index:0x0 pfn:0x777c4
head:ffffea0001ddf100 order:2 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 0000000000000000 dead000000000001 ffff888011841c80
raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask
pid 2972, tgid 2972 (udevadm), ts 11705893480, free_ts 9906278250
 prep_new_page mm/page_alloc.c:2532 [inline]
 get_page_from_freelist+0x109b/0x2ce0 mm/page_alloc.c:4283
 __alloc_pages+0x1c7/0x510 mm/page_alloc.c:5549
 alloc_pages+0x1a6/0x270 mm/mempolicy.c:2270
 alloc_slab_page mm/slub.c:1829 [inline]
 allocate_slab+0x27e/0x3d0 mm/slub.c:1974
 new_slab mm/slub.c:2034 [inline]
 ___slab_alloc+0x84f/0xe80 mm/slub.c:3036
 __slab_alloc.constprop.0+0x4d/0xa0 mm/slub.c:3123
 slab_alloc_node mm/slub.c:3214 [inline]
 slab_alloc mm/slub.c:3256 [inline]
 kmem_cache_alloc_trace+0x323/0x3e0 mm/slub.c:3287
 kmalloc include/linux/slab.h:600 [inline]
 kzalloc include/linux/slab.h:733 [inline]
 kernfs_fop_open+0x31a/0xec0 fs/kernfs/file.c:666
 do_dentry_open+0x6cc/0x13f0 fs/open.c:882
 do_open fs/namei.c:3557 [inline]
 path_openat+0x1c92/0x28f0 fs/namei.c:3691
 do_filp_open+0x1b6/0x400 fs/namei.c:3718
 do_sys_openat2+0x16d/0x4c0 fs/open.c:1310
 do_sys_open fs/open.c:1326 [inline]
 __do_sys_openat fs/open.c:1342 [inline]
 __se_sys_openat fs/open.c:1337 [inline]
 __x64_sys_openat+0x13f/0x1f0 fs/open.c:1337
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1449 [inline]
 free_pcp_prepare+0x5e4/0xd20 mm/page_alloc.c:1499
 free_unref_page_prepare mm/page_alloc.c:3380 [inline]
 free_unref_page+0x19/0x4d0 mm/page_alloc.c:3476
 free_contig_range+0xb1/0x180 mm/page_alloc.c:9457
 destroy_args+0xa8/0x646 mm/debug_vm_pgtable.c:1031
 debug_vm_pgtable+0x2945/0x29d6 mm/debug_vm_pgtable.c:1354
 do_one_initcall+0xfe/0x650 init/main.c:1296
 do_initcall_level init/main.c:1369 [inline]
 do_initcalls init/main.c:1385 [inline]
 do_basic_setup init/main.c:1404 [inline]
 kernel_init_freeable+0x6b1/0x73a init/main.c:1623
 kernel_init+0x1a/0x1d0 init/main.c:1512
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306

Memory state around the buggy address:
 ffff8880777c6280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880777c6300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880777c6380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                                                                ^
 ffff8880777c6400: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8880777c6480: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================

Writing to the address ptr will cause an out-of-bounds bug if the inode
allocation type is ICBTAG_FLAG_AD_SHORT (or ICBTAG_FLAG_AD_LONG), the
buffer head pointer is NULL, and iinfo->i_lenEAttr is 0. In this case,
the address ptr is iinfo->i_data - sizeof(struct short_ad), and the
out-of-bounds offset is the size of struct short_ad. This can be fixed
by adding the size of struct short_ad (or struct long_ad) to the address
ptr.

Reported-by: syzbot+908340a8367281960537@syzkaller.appspotmail.com
Fixes: 2c948b3f86e5 ("udf: Avoid IO in udf_clear_inode")
Signed-off-by: ZhangPeng <zhangpeng362@huawei.com>
---
 fs/udf/inode.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/udf/inode.c b/fs/udf/inode.c
index 8d06daed549f..abb3257b4c74 100644
--- a/fs/udf/inode.c
+++ b/fs/udf/inode.c
@@ -2090,10 +2090,15 @@ void udf_write_aext(struct inode *inode, struct extent_position *epos,
 	struct long_ad *lad;
 	struct udf_inode_info *iinfo = UDF_I(inode);
 
-	if (!epos->bh)
+	if (!epos->bh) {
 		ptr = iinfo->i_data + epos->offset -
 			udf_file_entry_alloc_offset(inode) +
 			iinfo->i_lenEAttr;
+		if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_SHORT)
+			ptr = ptr + sizeof(struct short_ad);
+		else if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_LONG)
+			ptr = ptr + sizeof(struct long_ad);
+	}
 	else
 		ptr = epos->bh->b_data + epos->offset;
 
-- 
2.25.1