On Wed 09-11-22 01:35:42, Peng Zhang wrote:

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_find_entry+0x8a5/0x14f0 fs/udf/namei.c:253 Write of size 105 at addr ffff8880123ff896 by task syz-executor323/3610

CPU: 0 PID: 3610 Comm: syz-executor323 Not tainted 6.1.0-rc2-syzkaller-00105-gb229b6ca5abb #0 Hardware name: Google Compute Engine/Google Compute Engine, BIOS Google 10/11/2022 Call Trace:

<TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x1b1/0x28e lib/dump_stack.c:106 print_address_description+0x74/0x340 mm/kasan/report.c:284 print_report+0x107/0x1f0 mm/kasan/report.c:395 kasan_report+0xcd/0x100 mm/kasan/report.c:495 kasan_check_range+0x2a7/0x2e0 mm/kasan/generic.c:189 memcpy+0x3c/0x60 mm/kasan/shadow.c:66 udf_find_entry+0x8a5/0x14f0 fs/udf/namei.c:253 udf_lookup+0xef/0x340 fs/udf/namei.c:309 lookup_open fs/namei.c:3391 [inline] open_last_lookups fs/namei.c:3481 [inline] path_openat+0x10e6/0x2df0 fs/namei.c:3710 do_filp_open+0x264/0x4f0 fs/namei.c:3740 do_sys_openat2+0x124/0x4e0 fs/open.c:1310 do_sys_open fs/open.c:1326 [inline] __do_sys_creat fs/open.c:1402 [inline] __se_sys_creat fs/open.c:1396 [inline] __x64_sys_creat+0x11f/0x160 fs/open.c:1396 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd RIP: 0033:0x7ffab0d164d9 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:00007ffe1a7e6bb8 EFLAGS: 00000246 ORIG_RAX: 0000000000000055 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007ffab0d164d9 RDX: 00007ffab0d164d9 RSI: 0000000000000000 RDI: 0000000020000180 RBP: 00007ffab0cd5a10 R08: 0000000000000000 R09: 0000000000000000 R10: 00005555573552c0 R11: 0000000000000246 R12: 00007ffab0cd5aa0 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 </TASK>

Allocated by task 3610: kasan_save_stack mm/kasan/common.c:45 [inline] kasan_set_track+0x3d/0x60 mm/kasan/common.c:52 ____kasan_kmalloc mm/kasan/common.c:371 [inline] __kasan_kmalloc+0x97/0xb0 mm/kasan/common.c:380 kmalloc include/linux/slab.h:576 [inline] udf_find_entry+0x7b6/0x14f0 fs/udf/namei.c:243 udf_lookup+0xef/0x340 fs/udf/namei.c:309 lookup_open fs/namei.c:3391 [inline] open_last_lookups fs/namei.c:3481 [inline] path_openat+0x10e6/0x2df0 fs/namei.c:3710 do_filp_open+0x264/0x4f0 fs/namei.c:3740 do_sys_openat2+0x124/0x4e0 fs/open.c:1310 do_sys_open fs/open.c:1326 [inline] __do_sys_creat fs/open.c:1402 [inline] __se_sys_creat fs/open.c:1396 [inline] __x64_sys_creat+0x11f/0x160 fs/open.c:1396 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd

The buggy address belongs to the object at ffff8880123ff800 which belongs to the cache kmalloc-256 of size 256 The buggy address is located 150 bytes inside of 256-byte region [ffff8880123ff800, ffff8880123ff900)

The buggy address belongs to the physical page: page:ffffea000048ff80 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x123fe head:ffffea000048ff80 order:1 compound_mapcount:0 compound_pincount:0 flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff) raw: 00fff00000010200 ffffea00004b8500 dead000000000003 ffff888012041b40 raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected page_owner tracks the page as allocated page last allocated via order 0, migratetype Unmovable, gfp_mask 0x0(), pid 1, tgid 1 (swapper/0), ts 1841222404, free_ts 0 create_dummy_stack mm/page_owner.c:67 [inline] register_early_stack+0x77/0xd0 mm/page_owner.c:83 init_page_owner+0x3a/0x731 mm/page_owner.c:93 kernel_init_freeable+0x41c/0x5d5 init/main.c:1629 kernel_init+0x19/0x2b0 init/main.c:1519 page_owner free stack trace missing

Memory state around the buggy address: ffff8880123ff780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff8880123ff800: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

...

ffff8880123ff880: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 06

                                                            ^

ffff8880123ff900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff8880123ff980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ==================================================================

Fix this by changing the memory size allocated for copy_name from UDF_NAME_LEN(254) to UDF_NAME_LEN_CS0(255), because the total length (lfi) of subsequent memcpy can be up to 255.

Reported-by: syzbot+69c9fdccc6dd08961d34@syzkaller.appspotmail.com Fixes: 066b9cded00b ("udf: Use separate buffer for copying split names") Signed-off-by: ZhangPeng zhangpeng362@huawei.com

Ah, good catch! Thanks for the fix! I've added it to my tree and will push it to Linus tomorrow.

Honza

---

fs/udf/namei.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/udf/namei.c b/fs/udf/namei.c index fb4c30e05245..ae7bc13a5298 100644 --- a/fs/udf/namei.c +++ b/fs/udf/namei.c @@ -240,7 +240,7 @@ static struct fileIdentDesc *udf_find_entry(struct inode *dir, poffset - lfi); else { if (!copy_name) {

• 			copy_name = kmalloc(UDF_NAME_LEN,
  

• 			copy_name = kmalloc(UDF_NAME_LEN_CS0,
  				    GFP_NOFS);
  		if (!copy_name) {
  			fi = ERR_PTR(-ENOMEM);
  

-- 2.25.1