[syzbot] KASAN: use-after-free Write in sctp_auth_shkey_hold

[syzbot] KASAN: use-after-free Write in sctp_auth_shkey_hold

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    5e437416 Merge branch 'dsa-mv88e6xxx-topaz-fixes'
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=14503bac300000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4cb84363d46e9fc3
dashboard link: https://syzkaller.appspot.com/bug?extid=b774577370208727d12b

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b774577370208727d12b@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
BUG: KASAN: use-after-free in atomic_fetch_add_relaxed include/asm-generic/atomic-instrumented.h:111 [inline]
BUG: KASAN: use-after-free in __refcount_add include/linux/refcount.h:193 [inline]
BUG: KASAN: use-after-free in __refcount_inc include/linux/refcount.h:250 [inline]
BUG: KASAN: use-after-free in refcount_inc include/linux/refcount.h:267 [inline]
BUG: KASAN: use-after-free in sctp_auth_shkey_hold+0x22/0xa0 net/sctp/auth.c:112
Write of size 4 at addr ffff88802053ad58 by task syz-executor.1/31590

CPU: 0 PID: 31590 Comm: syz-executor.1 Not tainted 5.13.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:96
 print_address_description.constprop.0.cold+0x6c/0x309 mm/kasan/report.c:233
 __kasan_report mm/kasan/report.c:419 [inline]
 kasan_report.cold+0x83/0xdf mm/kasan/report.c:436
 check_region_inline mm/kasan/generic.c:183 [inline]
 kasan_check_range+0x13d/0x180 mm/kasan/generic.c:189
 instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
 atomic_fetch_add_relaxed include/asm-generic/atomic-instrumented.h:111 [inline]
 __refcount_add include/linux/refcount.h:193 [inline]
 __refcount_inc include/linux/refcount.h:250 [inline]
 refcount_inc include/linux/refcount.h:267 [inline]
 sctp_auth_shkey_hold+0x22/0xa0 net/sctp/auth.c:112
 sctp_set_owner_w net/sctp/socket.c:131 [inline]
 sctp_sendmsg_to_asoc+0x152e/0x2180 net/sctp/socket.c:1865
 sctp_sendmsg+0x103b/0x1d30 net/sctp/socket.c:2027
 inet_sendmsg+0x99/0xe0 net/ipv4/af_inet.c:821
 sock_sendmsg_nosec net/socket.c:702 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:722
 ____sys_sendmsg+0x331/0x810 net/socket.c:2385
 ___sys_sendmsg+0xf3/0x170 net/socket.c:2439
 __sys_sendmmsg+0x195/0x470 net/socket.c:2525
 __do_sys_sendmmsg net/socket.c:2554 [inline]
 __se_sys_sendmmsg net/socket.c:2551 [inline]
 __x64_sys_sendmmsg+0x99/0x100 net/socket.c:2551
 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+0x44/0xae
RIP: 0033:0x4665d9
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 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f679ad9b188 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 000000000056bf80 RCX: 00000000004665d9
RDX: 0000000000000002 RSI: 0000000020002340 RDI: 0000000000000003
RBP: 00000000004bfcb9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf80
R13: 00007ffc95431f0f R14: 00007f679ad9b300 R15: 0000000000022000

Allocated by task 31590:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
 kasan_set_track mm/kasan/common.c:46 [inline]
 set_alloc_info mm/kasan/common.c:434 [inline]
 ____kasan_kmalloc mm/kasan/common.c:513 [inline]
 ____kasan_kmalloc mm/kasan/common.c:472 [inline]
 __kasan_kmalloc+0x9b/0xd0 mm/kasan/common.c:522
 kmalloc include/linux/slab.h:591 [inline]
 kzalloc include/linux/slab.h:721 [inline]
 sctp_auth_shkey_create+0x85/0x1f0 net/sctp/auth.c:84
 sctp_auth_asoc_copy_shkeys+0x1e8/0x350 net/sctp/auth.c:363
 sctp_association_init net/sctp/associola.c:257 [inline]
 sctp_association_new+0x1829/0x2250 net/sctp/associola.c:298
 sctp_connect_new_asoc+0x1ac/0x770 net/sctp/socket.c:1088
 __sctp_connect+0x3d0/0xc30 net/sctp/socket.c:1194
 sctp_connect net/sctp/socket.c:4804 [inline]
 sctp_inet_connect+0x15e/0x200 net/sctp/socket.c:4819
 __sys_connect_file+0x155/0x1a0 net/socket.c:1872
 __sys_connect+0x161/0x190 net/socket.c:1889
 __do_sys_connect net/socket.c:1899 [inline]
 __se_sys_connect net/socket.c:1896 [inline]
 __x64_sys_connect+0x6f/0xb0 net/socket.c:1896
 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+0x44/0xae

Freed by task 31590:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
 kasan_set_track+0x1c/0x30 mm/kasan/common.c:46
 kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:360
 ____kasan_slab_free mm/kasan/common.c:366 [inline]
 ____kasan_slab_free mm/kasan/common.c:328 [inline]
 __kasan_slab_free+0xfb/0x130 mm/kasan/common.c:374
 kasan_slab_free include/linux/kasan.h:229 [inline]
 slab_free_hook mm/slub.c:1639 [inline]
 slab_free_freelist_hook+0xdf/0x240 mm/slub.c:1664
 slab_free mm/slub.c:3224 [inline]
 kfree+0xeb/0x670 mm/slub.c:4268
 sctp_auth_shkey_destroy net/sctp/auth.c:101 [inline]
 sctp_auth_shkey_release+0x100/0x160 net/sctp/auth.c:107
 sctp_auth_set_key+0x508/0x6d0 net/sctp/auth.c:862
 sctp_setsockopt_auth_key net/sctp/socket.c:3643 [inline]
 sctp_setsockopt+0x4919/0xa5e0 net/sctp/socket.c:4682
 __sys_setsockopt+0x2db/0x610 net/socket.c:2152
 __do_sys_setsockopt net/socket.c:2163 [inline]
 __se_sys_setsockopt net/socket.c:2160 [inline]
 __x64_sys_setsockopt+0xba/0x150 net/socket.c:2160
 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+0x44/0xae

The buggy address belongs to the object at ffff88802053ad40
 which belongs to the cache kmalloc-32 of size 32
The buggy address is located 24 bytes inside of
 32-byte region [ffff88802053ad40, ffff88802053ad60)
The buggy address belongs to the page:
page:ffffea0000814e80 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2053a
flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000200 dead000000000100 dead000000000122 ffff888010841500
raw: 0000000000000000 0000000080400040 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 0x12c40(GFP_NOFS|__GFP_NOWARN|__GFP_NORETRY), pid 4873, ts 20137001110, free_ts 20080007470
 prep_new_page mm/page_alloc.c:2445 [inline]
 get_page_from_freelist+0xa72/0x2f80 mm/page_alloc.c:4178
 __alloc_pages+0x1b2/0x500 mm/page_alloc.c:5386
 alloc_pages+0x18c/0x2a0 mm/mempolicy.c:2272
 alloc_slab_page mm/slub.c:1702 [inline]
 allocate_slab+0x32b/0x4c0 mm/slub.c:1842
 new_slab mm/slub.c:1905 [inline]
 new_slab_objects mm/slub.c:2651 [inline]
 ___slab_alloc+0x4ba/0x820 mm/slub.c:2814
 __slab_alloc.constprop.0+0xa7/0xf0 mm/slub.c:2854
 slab_alloc_node mm/slub.c:2936 [inline]
 slab_alloc mm/slub.c:2978 [inline]
 __kmalloc+0x312/0x330 mm/slub.c:4106
 kmalloc include/linux/slab.h:596 [inline]
 kzalloc include/linux/slab.h:721 [inline]
 tomoyo_encode2.part.0+0xe9/0x3a0 security/tomoyo/realpath.c:45
 tomoyo_encode2 security/tomoyo/realpath.c:31 [inline]
 tomoyo_encode+0x28/0x50 security/tomoyo/realpath.c:80
 tomoyo_realpath_from_path+0x186/0x620 security/tomoyo/realpath.c:288
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_path_perm+0x21b/0x400 security/tomoyo/file.c:822
 security_inode_getattr+0xcf/0x140 security/security.c:1332
 vfs_getattr fs/stat.c:139 [inline]
 vfs_statx+0x164/0x390 fs/stat.c:207
 vfs_fstatat fs/stat.c:225 [inline]
 vfs_lstat include/linux/fs.h:3384 [inline]
 __do_sys_newlstat+0x91/0x110 fs/stat.c:380
 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+0x44/0xae
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1355 [inline]
 free_pcp_prepare+0x2c5/0x780 mm/page_alloc.c:1406
 free_unref_page_prepare mm/page_alloc.c:3341 [inline]
 free_unref_page+0x19/0x690 mm/page_alloc.c:3420
 qlink_free mm/kasan/quarantine.c:146 [inline]
 qlist_free_all+0x5a/0xc0 mm/kasan/quarantine.c:165
 kasan_quarantine_reduce+0x180/0x200 mm/kasan/quarantine.c:272
 __kasan_slab_alloc+0x8e/0xa0 mm/kasan/common.c:444
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slab.h:512 [inline]
 slab_alloc_node mm/slub.c:2970 [inline]
 slab_alloc mm/slub.c:2978 [inline]
 kmem_cache_alloc+0x29b/0x4a0 mm/slub.c:2983
 getname_flags.part.0+0x50/0x4f0 fs/namei.c:138
 getname_flags include/linux/audit.h:319 [inline]
 getname+0x8e/0xd0 fs/namei.c:209
 do_sys_openat2+0xf5/0x420 fs/open.c:1189
 do_sys_open fs/open.c:1211 [inline]
 __do_sys_open fs/open.c:1219 [inline]
 __se_sys_open fs/open.c:1215 [inline]
 __x64_sys_open+0x119/0x1c0 fs/open.c:1215
 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+0x44/0xae

Memory state around the buggy address:
 ffff88802053ac00: 00 00 00 02 fc fc fc fc fa fb fb fb fc fc fc fc
 ffff88802053ac80: 00 00 00 00 fc fc fc fc fa fb fb fb fc fc fc fc
>ffff88802053ad00: fb fb fb fb fc fc fc fc fa fb fb fb fc fc fc fc
                                                    ^
 ffff88802053ad80: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
 ffff88802053ae00: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
==================================================================


---
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Re: [syzbot] KASAN: use-after-free Write in sctp_auth_shkey_hold

[Xin Long]

On Mon, Jul 12, 2021 at 12:46 AM syzbot
<syzbot+b774577370208727d12b@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    5e437416 Merge branch 'dsa-mv88e6xxx-topaz-fixes'
> git tree:       net-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=14503bac300000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=4cb84363d46e9fc3
> dashboard link: https://syzkaller.appspot.com/bug?extid=b774577370208727d12b
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+b774577370208727d12b@syzkaller.appspotmail.com
>
> ==================================================================
> BUG: KASAN: use-after-free in instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
> BUG: KASAN: use-after-free in atomic_fetch_add_relaxed include/asm-generic/atomic-instrumented.h:111 [inline]
> BUG: KASAN: use-after-free in __refcount_add include/linux/refcount.h:193 [inline]
> BUG: KASAN: use-after-free in __refcount_inc include/linux/refcount.h:250 [inline]
> BUG: KASAN: use-after-free in refcount_inc include/linux/refcount.h:267 [inline]
> BUG: KASAN: use-after-free in sctp_auth_shkey_hold+0x22/0xa0 net/sctp/auth.c:112
> Write of size 4 at addr ffff88802053ad58 by task syz-executor.1/31590
>
> CPU: 0 PID: 31590 Comm: syz-executor.1 Not tainted 5.13.0-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:79 [inline]
>  dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:96
>  print_address_description.constprop.0.cold+0x6c/0x309 mm/kasan/report.c:233
>  __kasan_report mm/kasan/report.c:419 [inline]
>  kasan_report.cold+0x83/0xdf mm/kasan/report.c:436
>  check_region_inline mm/kasan/generic.c:183 [inline]
>  kasan_check_range+0x13d/0x180 mm/kasan/generic.c:189
>  instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
>  atomic_fetch_add_relaxed include/asm-generic/atomic-instrumented.h:111 [inline]
>  __refcount_add include/linux/refcount.h:193 [inline]
>  __refcount_inc include/linux/refcount.h:250 [inline]
>  refcount_inc include/linux/refcount.h:267 [inline]
>  sctp_auth_shkey_hold+0x22/0xa0 net/sctp/auth.c:112
>  sctp_set_owner_w net/sctp/socket.c:131 [inline]
>  sctp_sendmsg_to_asoc+0x152e/0x2180 net/sctp/socket.c:1865
>  sctp_sendmsg+0x103b/0x1d30 net/sctp/socket.c:2027
>  inet_sendmsg+0x99/0xe0 net/ipv4/af_inet.c:821
>  sock_sendmsg_nosec net/socket.c:702 [inline]
>  sock_sendmsg+0xcf/0x120 net/socket.c:722
>  ____sys_sendmsg+0x331/0x810 net/socket.c:2385
>  ___sys_sendmsg+0xf3/0x170 net/socket.c:2439
>  __sys_sendmmsg+0x195/0x470 net/socket.c:2525
>  __do_sys_sendmmsg net/socket.c:2554 [inline]
>  __se_sys_sendmmsg net/socket.c:2551 [inline]
>  __x64_sys_sendmmsg+0x99/0x100 net/socket.c:2551
>  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+0x44/0xae
> RIP: 0033:0x4665d9
> 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 bc ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007f679ad9b188 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
> RAX: ffffffffffffffda RBX: 000000000056bf80 RCX: 00000000004665d9
> RDX: 0000000000000002 RSI: 0000000020002340 RDI: 0000000000000003
> RBP: 00000000004bfcb9 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf80
> R13: 00007ffc95431f0f R14: 00007f679ad9b300 R15: 0000000000022000
>
> Allocated by task 31590:
>  kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
>  kasan_set_track mm/kasan/common.c:46 [inline]
>  set_alloc_info mm/kasan/common.c:434 [inline]
>  ____kasan_kmalloc mm/kasan/common.c:513 [inline]
>  ____kasan_kmalloc mm/kasan/common.c:472 [inline]
>  __kasan_kmalloc+0x9b/0xd0 mm/kasan/common.c:522
>  kmalloc include/linux/slab.h:591 [inline]
>  kzalloc include/linux/slab.h:721 [inline]
>  sctp_auth_shkey_create+0x85/0x1f0 net/sctp/auth.c:84
>  sctp_auth_asoc_copy_shkeys+0x1e8/0x350 net/sctp/auth.c:363
>  sctp_association_init net/sctp/associola.c:257 [inline]
>  sctp_association_new+0x1829/0x2250 net/sctp/associola.c:298
>  sctp_connect_new_asoc+0x1ac/0x770 net/sctp/socket.c:1088
>  __sctp_connect+0x3d0/0xc30 net/sctp/socket.c:1194
>  sctp_connect net/sctp/socket.c:4804 [inline]
>  sctp_inet_connect+0x15e/0x200 net/sctp/socket.c:4819
>  __sys_connect_file+0x155/0x1a0 net/socket.c:1872
>  __sys_connect+0x161/0x190 net/socket.c:1889
>  __do_sys_connect net/socket.c:1899 [inline]
>  __se_sys_connect net/socket.c:1896 [inline]
>  __x64_sys_connect+0x6f/0xb0 net/socket.c:1896
>  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+0x44/0xae
>
> Freed by task 31590:
>  kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
>  kasan_set_track+0x1c/0x30 mm/kasan/common.c:46
>  kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:360
>  ____kasan_slab_free mm/kasan/common.c:366 [inline]
>  ____kasan_slab_free mm/kasan/common.c:328 [inline]
>  __kasan_slab_free+0xfb/0x130 mm/kasan/common.c:374
>  kasan_slab_free include/linux/kasan.h:229 [inline]
>  slab_free_hook mm/slub.c:1639 [inline]
>  slab_free_freelist_hook+0xdf/0x240 mm/slub.c:1664
>  slab_free mm/slub.c:3224 [inline]
>  kfree+0xeb/0x670 mm/slub.c:4268
>  sctp_auth_shkey_destroy net/sctp/auth.c:101 [inline]
>  sctp_auth_shkey_release+0x100/0x160 net/sctp/auth.c:107
>  sctp_auth_set_key+0x508/0x6d0 net/sctp/auth.c:862
It seems caused by not updating asoc->shkey when the old key is being deleted:

diff --git a/net/sctp/auth.c b/net/sctp/auth.c
index 6f8319b..d095247 100644
--- a/net/sctp/auth.c
+++ b/net/sctp/auth.c
@@ -858,6 +858,8 @@ int sctp_auth_set_key(struct sctp_endpoint *ep,
        cur_key->key = key;

        if (replace) {
+               if (asoc && asoc->shkey == shkey)
+                       asoc->shkey = cur_key;
                list_del_init(&shkey->key_list);
                sctp_auth_shkey_release(shkey);
        }

>  sctp_setsockopt_auth_key net/sctp/socket.c:3643 [inline]
>  sctp_setsockopt+0x4919/0xa5e0 net/sctp/socket.c:4682
>  __sys_setsockopt+0x2db/0x610 net/socket.c:2152
>  __do_sys_setsockopt net/socket.c:2163 [inline]
>  __se_sys_setsockopt net/socket.c:2160 [inline]
>  __x64_sys_setsockopt+0xba/0x150 net/socket.c:2160
>  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+0x44/0xae
>
> The buggy address belongs to the object at ffff88802053ad40
>  which belongs to the cache kmalloc-32 of size 32
> The buggy address is located 24 bytes inside of
>  32-byte region [ffff88802053ad40, ffff88802053ad60)
> The buggy address belongs to the page:
> page:ffffea0000814e80 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2053a
> flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
> raw: 00fff00000000200 dead000000000100 dead000000000122 ffff888010841500
> raw: 0000000000000000 0000000080400040 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 0x12c40(GFP_NOFS|__GFP_NOWARN|__GFP_NORETRY), pid 4873, ts 20137001110, free_ts 20080007470
>  prep_new_page mm/page_alloc.c:2445 [inline]
>  get_page_from_freelist+0xa72/0x2f80 mm/page_alloc.c:4178
>  __alloc_pages+0x1b2/0x500 mm/page_alloc.c:5386
>  alloc_pages+0x18c/0x2a0 mm/mempolicy.c:2272
>  alloc_slab_page mm/slub.c:1702 [inline]
>  allocate_slab+0x32b/0x4c0 mm/slub.c:1842
>  new_slab mm/slub.c:1905 [inline]
>  new_slab_objects mm/slub.c:2651 [inline]
>  ___slab_alloc+0x4ba/0x820 mm/slub.c:2814
>  __slab_alloc.constprop.0+0xa7/0xf0 mm/slub.c:2854
>  slab_alloc_node mm/slub.c:2936 [inline]
>  slab_alloc mm/slub.c:2978 [inline]
>  __kmalloc+0x312/0x330 mm/slub.c:4106
>  kmalloc include/linux/slab.h:596 [inline]
>  kzalloc include/linux/slab.h:721 [inline]
>  tomoyo_encode2.part.0+0xe9/0x3a0 security/tomoyo/realpath.c:45
>  tomoyo_encode2 security/tomoyo/realpath.c:31 [inline]
>  tomoyo_encode+0x28/0x50 security/tomoyo/realpath.c:80
>  tomoyo_realpath_from_path+0x186/0x620 security/tomoyo/realpath.c:288
>  tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
>  tomoyo_path_perm+0x21b/0x400 security/tomoyo/file.c:822
>  security_inode_getattr+0xcf/0x140 security/security.c:1332
>  vfs_getattr fs/stat.c:139 [inline]
>  vfs_statx+0x164/0x390 fs/stat.c:207
>  vfs_fstatat fs/stat.c:225 [inline]
>  vfs_lstat include/linux/fs.h:3384 [inline]
>  __do_sys_newlstat+0x91/0x110 fs/stat.c:380
>  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+0x44/0xae
> page last free stack trace:
>  reset_page_owner include/linux/page_owner.h:24 [inline]
>  free_pages_prepare mm/page_alloc.c:1355 [inline]
>  free_pcp_prepare+0x2c5/0x780 mm/page_alloc.c:1406
>  free_unref_page_prepare mm/page_alloc.c:3341 [inline]
>  free_unref_page+0x19/0x690 mm/page_alloc.c:3420
>  qlink_free mm/kasan/quarantine.c:146 [inline]
>  qlist_free_all+0x5a/0xc0 mm/kasan/quarantine.c:165
>  kasan_quarantine_reduce+0x180/0x200 mm/kasan/quarantine.c:272
>  __kasan_slab_alloc+0x8e/0xa0 mm/kasan/common.c:444
>  kasan_slab_alloc include/linux/kasan.h:253 [inline]
>  slab_post_alloc_hook mm/slab.h:512 [inline]
>  slab_alloc_node mm/slub.c:2970 [inline]
>  slab_alloc mm/slub.c:2978 [inline]
>  kmem_cache_alloc+0x29b/0x4a0 mm/slub.c:2983
>  getname_flags.part.0+0x50/0x4f0 fs/namei.c:138
>  getname_flags include/linux/audit.h:319 [inline]
>  getname+0x8e/0xd0 fs/namei.c:209
>  do_sys_openat2+0xf5/0x420 fs/open.c:1189
>  do_sys_open fs/open.c:1211 [inline]
>  __do_sys_open fs/open.c:1219 [inline]
>  __se_sys_open fs/open.c:1215 [inline]
>  __x64_sys_open+0x119/0x1c0 fs/open.c:1215
>  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+0x44/0xae
>
> Memory state around the buggy address:
>  ffff88802053ac00: 00 00 00 02 fc fc fc fc fa fb fb fb fc fc fc fc
>  ffff88802053ac80: 00 00 00 00 fc fc fc fc fa fb fb fb fc fc fc fc
> >ffff88802053ad00: fb fb fb fb fc fc fc fc fa fb fb fb fc fc fc fc
>                                                     ^
>  ffff88802053ad80: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
>  ffff88802053ae00: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
> ==================================================================
>
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@googlegroups.com.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

Re: [syzbot] KASAN: use-after-free Write in sctp_auth_shkey_hold

[Xin Long]

On Sat, Jul 17, 2021 at 12:57 AM Hillf Danton <hdanton@sina.com> wrote:
>
> On Fri, 16 Jul 2021 16:01:01 -0400 Xin Long wrote:
> >On Mon, Jul 12, 2021 at 12:46 AM syzbot wrote:
> >>
> >> Hello,
> >>
> >> syzbot found the following issue on:
> >>
> >> HEAD commit:    5e437416 Merge branch 'dsa-mv88e6xxx-topaz-fixes'
> >> git tree:       net-next
> >> console output: https://syzkaller.appspot.com/x/log.txt?x=14503bac300000
> >> kernel config:  https://syzkaller.appspot.com/x/.config?x=4cb84363d46e9fc3
> >> dashboard link: https://syzkaller.appspot.com/bug?extid=b774577370208727d12b
> >>
> >> Unfortunately, I don't have any reproducer for this issue yet.
> >>
> >> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> >> Reported-by: syzbot+b774577370208727d12b@syzkaller.appspotmail.com
> >>
> >> ==================================================================
> >> BUG: KASAN: use-after-free in instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
> >> BUG: KASAN: use-after-free in atomic_fetch_add_relaxed include/asm-generic/atomic-instrumented.h:111 [inline]
> >> BUG: KASAN: use-after-free in __refcount_add include/linux/refcount.h:193 [inline]
> >> BUG: KASAN: use-after-free in __refcount_inc include/linux/refcount.h:250 [inline]
> >> BUG: KASAN: use-after-free in refcount_inc include/linux/refcount.h:267 [inline]
> >> BUG: KASAN: use-after-free in sctp_auth_shkey_hold+0x22/0xa0 net/sctp/auth.c:112
> >> Write of size 4 at addr ffff88802053ad58 by task syz-executor.1/31590
> >>
> >> CPU: 0 PID: 31590 Comm: syz-executor.1 Not tainted 5.13.0-syzkaller #0
> >> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> >> Call Trace:
> >>  __dump_stack lib/dump_stack.c:79 [inline]
> >>  dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:96
> >>  print_address_description.constprop.0.cold+0x6c/0x309 mm/kasan/report.c:233
> >>  __kasan_report mm/kasan/report.c:419 [inline]
> >>  kasan_report.cold+0x83/0xdf mm/kasan/report.c:436
> >>  check_region_inline mm/kasan/generic.c:183 [inline]
> >>  kasan_check_range+0x13d/0x180 mm/kasan/generic.c:189
> >>  instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
> >>  atomic_fetch_add_relaxed include/asm-generic/atomic-instrumented.h:111 [inline]
> >>  __refcount_add include/linux/refcount.h:193 [inline]
> >>  __refcount_inc include/linux/refcount.h:250 [inline]
> >>  refcount_inc include/linux/refcount.h:267 [inline]
> >>  sctp_auth_shkey_hold+0x22/0xa0 net/sctp/auth.c:112
> >>  sctp_set_owner_w net/sctp/socket.c:131 [inline]
>
> 1)      datamsg = sctp_datamsg_from_user(asoc, sinfo, &msg->msg_iter);
>
> Chunks are built with sock lock held(lock_sock(sk);).
>
> >>  sctp_sendmsg_to_asoc+0x152e/0x2180 net/sctp/socket.c:1865
> >>  sctp_sendmsg+0x103b/0x1d30 net/sctp/socket.c:2027
> >>  inet_sendmsg+0x99/0xe0 net/ipv4/af_inet.c:821
> >>  sock_sendmsg_nosec net/socket.c:702 [inline]
> >>  sock_sendmsg+0xcf/0x120 net/socket.c:722
> >>  ____sys_sendmsg+0x331/0x810 net/socket.c:2385
> >>  ___sys_sendmsg+0xf3/0x170 net/socket.c:2439
> >>  __sys_sendmmsg+0x195/0x470 net/socket.c:2525
> >>  __do_sys_sendmmsg net/socket.c:2554 [inline]
> >>  __se_sys_sendmmsg net/socket.c:2551 [inline]
> >>  __x64_sys_sendmmsg+0x99/0x100 net/socket.c:2551
> >>  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+0x44/0xae
> >> RIP: 0033:0x4665d9
> >> 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 bc ff ff ff f7 d8 64 89 01 48
> >> RSP: 002b:00007f679ad9b188 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
> >> RAX: ffffffffffffffda RBX: 000000000056bf80 RCX: 00000000004665d9
> >> RDX: 0000000000000002 RSI: 0000000020002340 RDI: 0000000000000003
> >> RBP: 00000000004bfcb9 R08: 0000000000000000 R09: 0000000000000000
> >> R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf80
> >> R13: 00007ffc95431f0f R14: 00007f679ad9b300 R15: 0000000000022000
> >>
> >> Allocated by task 31590:
> >>  kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
> >>  kasan_set_track mm/kasan/common.c:46 [inline]
> >>  set_alloc_info mm/kasan/common.c:434 [inline]
> >>  ____kasan_kmalloc mm/kasan/common.c:513 [inline]
> >>  ____kasan_kmalloc mm/kasan/common.c:472 [inline]
> >>  __kasan_kmalloc+0x9b/0xd0 mm/kasan/common.c:522
> >>  kmalloc include/linux/slab.h:591 [inline]
> >>  kzalloc include/linux/slab.h:721 [inline]
> >>  sctp_auth_shkey_create+0x85/0x1f0 net/sctp/auth.c:84
> >>  sctp_auth_asoc_copy_shkeys+0x1e8/0x350 net/sctp/auth.c:363
> >>  sctp_association_init net/sctp/associola.c:257 [inline]
> >>  sctp_association_new+0x1829/0x2250 net/sctp/associola.c:298
> >>  sctp_connect_new_asoc+0x1ac/0x770 net/sctp/socket.c:1088
> >>  __sctp_connect+0x3d0/0xc30 net/sctp/socket.c:1194
> >>  sctp_connect net/sctp/socket.c:4804 [inline]
> >>  sctp_inet_connect+0x15e/0x200 net/sctp/socket.c:4819
> >>  __sys_connect_file+0x155/0x1a0 net/socket.c:1872
> >>  __sys_connect+0x161/0x190 net/socket.c:1889
> >>  __do_sys_connect net/socket.c:1899 [inline]
> >>  __se_sys_connect net/socket.c:1896 [inline]
> >>  __x64_sys_connect+0x6f/0xb0 net/socket.c:1896
> >>  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+0x44/0xae
> >>
> >> Freed by task 31590:
> >>  kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
> >>  kasan_set_track+0x1c/0x30 mm/kasan/common.c:46
> >>  kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:360
> >>  ____kasan_slab_free mm/kasan/common.c:366 [inline]
> >>  ____kasan_slab_free mm/kasan/common.c:328 [inline]
> >>  __kasan_slab_free+0xfb/0x130 mm/kasan/common.c:374
> >>  kasan_slab_free include/linux/kasan.h:229 [inline]
> >>  slab_free_hook mm/slub.c:1639 [inline]
> >>  slab_free_freelist_hook+0xdf/0x240 mm/slub.c:1664
> >>  slab_free mm/slub.c:3224 [inline]
> >>  kfree+0xeb/0x670 mm/slub.c:4268
> >>  sctp_auth_shkey_destroy net/sctp/auth.c:101 [inline]
> >>  sctp_auth_shkey_release+0x100/0x160 net/sctp/auth.c:107
> >>  sctp_auth_set_key+0x508/0x6d0 net/sctp/auth.c:862
> >>
> >It seems caused by not updating asoc->shkey when the old key is being deleted:
>
> Nope, see 1) and 2).
It's not about lock protection.

asoc->shkey became invalid after 'shkey' (== asoc->shkey)  is released
in sctp_auth_set_key() and all chunks freed its shkey.
the crash is triggered by this invalid asoc->shkey used.

We should fix it by updating asoc->shkey when it's being released,
more accurately:

@@ -860,6 +860,8 @@ int sctp_auth_set_key(struct sctp_endpoint *ep,
        if (replace) {
                list_del_init(&shkey->key_list);
                sctp_auth_shkey_release(shkey);
+               if (asoc && asoc->active_key_id == auth_key->sca_keynumber)
+                       sctp_auth_asoc_init_active_key(asoc, GFP_KERNEL);
        }

>
> >
> >diff --git a/net/sctp/auth.c b/net/sctp/auth.c
> >index 6f8319b..d095247 100644
> >--- a/net/sctp/auth.c
> >+++ b/net/sctp/auth.c
> >@@ -858,6 +858,8 @@ int sctp_auth_set_key(struct sctp_endpoint *ep,
> >        cur_key->key = key;
> >
> >        if (replace) {
> >+               if (asoc && asoc->shkey == shkey)
> >+                       asoc->shkey = cur_key;
> >                list_del_init(&shkey->key_list);
> >                sctp_auth_shkey_release(shkey);
> >        }
> >
> >>  sctp_setsockopt_auth_key net/sctp/socket.c:3643 [inline]
>
> 2)  lock_sock(sk);
>
> >>  sctp_setsockopt+0x4919/0xa5e0 net/sctp/socket.c:4682
> >>  __sys_setsockopt+0x2db/0x610 net/socket.c:2152
> >>  __do_sys_setsockopt net/socket.c:2163 [inline]
> >>  __se_sys_setsockopt net/socket.c:2160 [inline]
> >>  __x64_sys_setsockopt+0xba/0x150 net/socket.c:2160
> >>  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+0x44/0xae

Re: [syzbot] KASAN: use-after-free Write in sctp_auth_shkey_hold

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit:    0d6835ffe50c net: phy: Fix data type in DP83822 dp8382x_di..
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=15b3f6f2300000
kernel config:  https://syzkaller.appspot.com/x/.config?x=da140227e4f25b17
dashboard link: https://syzkaller.appspot.com/bug?extid=b774577370208727d12b
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11f6055c300000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=162a9040300000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b774577370208727d12b@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
BUG: KASAN: use-after-free in atomic_fetch_add_relaxed include/asm-generic/atomic-instrumented.h:111 [inline]
BUG: KASAN: use-after-free in __refcount_add include/linux/refcount.h:193 [inline]
BUG: KASAN: use-after-free in __refcount_inc include/linux/refcount.h:250 [inline]
BUG: KASAN: use-after-free in refcount_inc include/linux/refcount.h:267 [inline]
BUG: KASAN: use-after-free in sctp_auth_shkey_hold+0x22/0xa0 net/sctp/auth.c:112
Write of size 4 at addr ffff888027eb5018 by task syz-executor843/8468

CPU: 1 PID: 8468 Comm: syz-executor843 Not tainted 5.14.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:105
 print_address_description.constprop.0.cold+0x6c/0x309 mm/kasan/report.c:233
 __kasan_report mm/kasan/report.c:419 [inline]
 kasan_report.cold+0x83/0xdf mm/kasan/report.c:436
 check_region_inline mm/kasan/generic.c:183 [inline]
 kasan_check_range+0x13d/0x180 mm/kasan/generic.c:189
 instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
 atomic_fetch_add_relaxed include/asm-generic/atomic-instrumented.h:111 [inline]
 __refcount_add include/linux/refcount.h:193 [inline]
 __refcount_inc include/linux/refcount.h:250 [inline]
 refcount_inc include/linux/refcount.h:267 [inline]
 sctp_auth_shkey_hold+0x22/0xa0 net/sctp/auth.c:112
 sctp_set_owner_w net/sctp/socket.c:131 [inline]
 sctp_sendmsg_to_asoc+0x152e/0x2180 net/sctp/socket.c:1865
 sctp_sendmsg+0x103b/0x1d30 net/sctp/socket.c:2027
 inet_sendmsg+0x99/0xe0 net/ipv4/af_inet.c:821
 sock_sendmsg_nosec net/socket.c:703 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:723
 __sys_sendto+0x21c/0x320 net/socket.c:2019
 __do_sys_sendto net/socket.c:2031 [inline]
 __se_sys_sendto net/socket.c:2027 [inline]
 __x64_sys_sendto+0xdd/0x1b0 net/socket.c:2027
 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+0x44/0xae
RIP: 0033:0x43efe9
Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 00 00 00 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:00007fff191e50c8 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 0100000000000000 RCX: 000000000043efe9
RDX: 000000000000ffa0 RSI: 0000000020000140 RDI: 0000000000000003
RBP: 0000000000402fd0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000403060
R13: 0000000000000000 R14: 00000000004ac018 R15: 0000000000400488

Allocated by task 8468:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
 kasan_set_track mm/kasan/common.c:46 [inline]
 set_alloc_info mm/kasan/common.c:434 [inline]
 ____kasan_kmalloc mm/kasan/common.c:513 [inline]
 ____kasan_kmalloc mm/kasan/common.c:472 [inline]
 __kasan_kmalloc+0x9b/0xd0 mm/kasan/common.c:522
 kmalloc include/linux/slab.h:591 [inline]
 kzalloc include/linux/slab.h:721 [inline]
 sctp_auth_shkey_create+0x85/0x1f0 net/sctp/auth.c:84
 sctp_auth_asoc_copy_shkeys+0x1e8/0x350 net/sctp/auth.c:363
 sctp_association_init net/sctp/associola.c:257 [inline]
 sctp_association_new+0x1829/0x2250 net/sctp/associola.c:298
 sctp_connect_new_asoc+0x1ac/0x770 net/sctp/socket.c:1088
 __sctp_connect+0x3d0/0xc30 net/sctp/socket.c:1194
 sctp_connect net/sctp/socket.c:4804 [inline]
 sctp_inet_connect+0x15e/0x200 net/sctp/socket.c:4819
 __sys_connect_file+0x155/0x1a0 net/socket.c:1879
 __sys_connect+0x161/0x190 net/socket.c:1896
 __do_sys_connect net/socket.c:1906 [inline]
 __se_sys_connect net/socket.c:1903 [inline]
 __x64_sys_connect+0x6f/0xb0 net/socket.c:1903
 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+0x44/0xae

Freed by task 8468:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
 kasan_set_track+0x1c/0x30 mm/kasan/common.c:46
 kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:360
 ____kasan_slab_free mm/kasan/common.c:366 [inline]
 ____kasan_slab_free mm/kasan/common.c:328 [inline]
 __kasan_slab_free+0xfb/0x130 mm/kasan/common.c:374
 kasan_slab_free include/linux/kasan.h:229 [inline]
 slab_free_hook mm/slub.c:1650 [inline]
 slab_free_freelist_hook+0xdf/0x240 mm/slub.c:1675
 slab_free mm/slub.c:3235 [inline]
 kfree+0xeb/0x650 mm/slub.c:4295
 sctp_auth_shkey_destroy net/sctp/auth.c:101 [inline]
 sctp_auth_shkey_release+0x100/0x160 net/sctp/auth.c:107
 sctp_auth_set_key+0x508/0x6d0 net/sctp/auth.c:862
 sctp_setsockopt_auth_key net/sctp/socket.c:3643 [inline]
 sctp_setsockopt+0x4919/0xa5e0 net/sctp/socket.c:4682
 __sys_setsockopt+0x2db/0x610 net/socket.c:2159
 __do_sys_setsockopt net/socket.c:2170 [inline]
 __se_sys_setsockopt net/socket.c:2167 [inline]
 __x64_sys_setsockopt+0xba/0x150 net/socket.c:2167
 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+0x44/0xae

The buggy address belongs to the object at ffff888027eb5000
 which belongs to the cache kmalloc-32 of size 32
The buggy address is located 24 bytes inside of
 32-byte region [ffff888027eb5000, ffff888027eb5020)
The buggy address belongs to the page:
page:ffffea00009fad40 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x27eb5
flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000200 ffffea000056e240 0000000d0000000d ffff888010841500
raw: 0000000000000000 0000000080400040 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 0x12c40(GFP_NOFS|__GFP_NOWARN|__GFP_NORETRY), pid 1, ts 15828671942, free_ts 14464854502
 prep_new_page mm/page_alloc.c:2433 [inline]
 get_page_from_freelist+0xa72/0x2f80 mm/page_alloc.c:4166
 __alloc_pages+0x1b2/0x500 mm/page_alloc.c:5374
 alloc_pages+0x18c/0x2a0 mm/mempolicy.c:2244
 alloc_slab_page mm/slub.c:1713 [inline]
 allocate_slab+0x32b/0x4c0 mm/slub.c:1853
 new_slab mm/slub.c:1916 [inline]
 new_slab_objects mm/slub.c:2662 [inline]
 ___slab_alloc+0x4ba/0x820 mm/slub.c:2825
 __slab_alloc.constprop.0+0xa7/0xf0 mm/slub.c:2865
 slab_alloc_node mm/slub.c:2947 [inline]
 slab_alloc mm/slub.c:2989 [inline]
 __kmalloc+0x312/0x330 mm/slub.c:4133
 kmalloc include/linux/slab.h:596 [inline]
 kzalloc include/linux/slab.h:721 [inline]
 tomoyo_encode2.part.0+0xe9/0x3a0 security/tomoyo/realpath.c:45
 tomoyo_encode2 security/tomoyo/realpath.c:31 [inline]
 tomoyo_encode+0x28/0x50 security/tomoyo/realpath.c:80
 tomoyo_realpath_from_path+0x186/0x620 security/tomoyo/realpath.c:288
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_check_open_permission+0x272/0x380 security/tomoyo/file.c:771
 tomoyo_file_open security/tomoyo/tomoyo.c:311 [inline]
 tomoyo_file_open+0xa3/0xd0 security/tomoyo/tomoyo.c:306
 security_file_open+0x52/0x4f0 security/security.c:1633
 do_dentry_open+0x353/0x11d0 fs/open.c:813
 do_open fs/namei.c:3374 [inline]
 path_openat+0x1c23/0x27f0 fs/namei.c:3507
 do_filp_open+0x1aa/0x400 fs/namei.c:3534
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1343 [inline]
 free_pcp_prepare+0x2c5/0x780 mm/page_alloc.c:1394
 free_unref_page_prepare mm/page_alloc.c:3329 [inline]
 free_unref_page+0x19/0x690 mm/page_alloc.c:3408
 kasan_depopulate_vmalloc_pte+0x5c/0x70 mm/kasan/shadow.c:375
 apply_to_pte_range mm/memory.c:2532 [inline]
 apply_to_pmd_range mm/memory.c:2576 [inline]
 apply_to_pud_range mm/memory.c:2612 [inline]
 apply_to_p4d_range mm/memory.c:2648 [inline]
 __apply_to_page_range+0x694/0x1080 mm/memory.c:2682
 kasan_release_vmalloc+0xa7/0xc0 mm/kasan/shadow.c:485
 __purge_vmap_area_lazy+0x8f9/0x1c50 mm/vmalloc.c:1670
 _vm_unmap_aliases.part.0+0x3f0/0x500 mm/vmalloc.c:2073
 _vm_unmap_aliases mm/vmalloc.c:2047 [inline]
 vm_unmap_aliases+0x47/0x50 mm/vmalloc.c:2096
 change_page_attr_set_clr+0x241/0x500 arch/x86/mm/pat/set_memory.c:1740
 change_page_attr_set arch/x86/mm/pat/set_memory.c:1790 [inline]
 set_memory_nx+0xb2/0x110 arch/x86/mm/pat/set_memory.c:1938
 free_init_pages+0x73/0xc0 arch/x86/mm/init.c:887
 kernel_init+0x24/0x1d0 init/main.c:1491
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

Memory state around the buggy address:
 ffff888027eb4f00: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
 ffff888027eb4f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888027eb5000: fa fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
                            ^
 ffff888027eb5080: fb fb fb fb fc fc fc fc fa fb fb fb fc fc fc fc
 ffff888027eb5100: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
==================================================================

Re: [syzbot] KASAN: use-after-free Write in sctp_auth_shkey_hold

[syzbot]

syzbot has bisected this issue to:

commit 56dd525abd56f7acd7b44a52935726e3ada4916c
Author: Xin Long <lucien.xin@gmail.com>
Date:   Mon Aug 19 14:02:49 2019 +0000

    sctp: add SCTP_AUTH_SUPPORTED sockopt

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=162bdf22300000
start commit:   6f20c8adb181 net/tcp_fastopen: fix data races around tfo_a..
git tree:       net
final oops:     https://syzkaller.appspot.com/x/report.txt?x=152bdf22300000
console output: https://syzkaller.appspot.com/x/log.txt?x=112bdf22300000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6da37c7627210105
dashboard link: https://syzkaller.appspot.com/bug?extid=b774577370208727d12b
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12d37b4a300000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=114bd0ea300000

Reported-by: syzbot+b774577370208727d12b@syzkaller.appspotmail.com
Fixes: 56dd525abd56 ("sctp: add SCTP_AUTH_SUPPORTED sockopt")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection