Re: [syzbot] [keyrings?] [lsm?] KASAN: slab-use-after-free Read in key_put

[Suraj Sonawane <surajsonawane0215@gmail.com>]

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#syz test

On Mon, Nov 18, 2024 at 9:57 PM syzbot <
syzbot+6105ffc1ded71d194d6d@syzkaller.appspotmail.com> wrote:

> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    adc218676eef Linux 6.12
> git tree:       upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=16c672e8580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=55f8591b98dd132
> dashboard link:
> https://syzkaller.appspot.com/bug?extid=6105ffc1ded71d194d6d
> compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for
> Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12dbbb5f980000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=11c672e8580000
>
> Downloadable assets:
> disk image:
> https://storage.googleapis.com/syzbot-assets/2362200b664b/disk-adc21867.raw.xz
> vmlinux:
> https://storage.googleapis.com/syzbot-assets/866b8b236466/vmlinux-adc21867.xz
> kernel image:
> https://storage.googleapis.com/syzbot-assets/607680582dad/bzImage-adc21867.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the
> commit:
> Reported-by: syzbot+6105ffc1ded71d194d6d@syzkaller.appspotmail.com
>
> trusted_key: encrypted_key: insufficient parameters specified
> ==================================================================
> BUG: KASAN: slab-use-after-free in key_put security/keys/key.c:657 [inline]
> BUG: KASAN: slab-use-after-free in key_put+0x288/0x2a0
> security/keys/key.c:646
> Read of size 8 at addr ffff888079173b00 by task syz-executor356/7162
>
> CPU: 0 UID: 0 PID: 7162 Comm: syz-executor356 Not tainted 6.12.0-syzkaller
> #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 10/30/2024
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:94 [inline]
>  dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
>  print_address_description mm/kasan/report.c:377 [inline]
>  print_report+0xc3/0x620 mm/kasan/report.c:488
>  kasan_report+0xd9/0x110 mm/kasan/report.c:601
>  key_put security/keys/key.c:657 [inline]
>  key_put+0x288/0x2a0 security/keys/key.c:646
>  __key_create_or_update+0x92b/0xe10 security/keys/key.c:940
>  key_create_or_update+0x42/0x60 security/keys/key.c:1018
>  __do_sys_add_key+0x29c/0x460 security/keys/keyctl.c:134
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7f410659a399
> Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 51 18 00 00 90 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 b0 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007f4106552218 EFLAGS: 00000246 ORIG_RAX: 00000000000000f8
> RAX: ffffffffffffffda RBX: 00007f4106621328 RCX: 00007f410659a399
> RDX: 0000000020000100 RSI: 0000000020000180 RDI: 0000000020000140
> RBP: 00007f4106621320 R08: 00000000fffffffe R09: 0000000000000000
> R10: 00000000000000ca R11: 0000000000000246 R12: 00007f41065ee074
> R13: 0072736d2f232f75 R14: 7570632f7665642f R15: 6574707972636e65
>  </TASK>
>
> Allocated by task 7162:
>  kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
>  kasan_save_track+0x14/0x30 mm/kasan/common.c:68
>  unpoison_slab_object mm/kasan/common.c:319 [inline]
>  __kasan_slab_alloc+0x89/0x90 mm/kasan/common.c:345
>  kasan_slab_alloc include/linux/kasan.h:247 [inline]
>  slab_post_alloc_hook mm/slub.c:4085 [inline]
>  slab_alloc_node mm/slub.c:4134 [inline]
>  kmem_cache_alloc_noprof+0x121/0x2f0 mm/slub.c:4141
>  key_alloc+0x3e3/0x13a0 security/keys/key.c:277
>  __key_create_or_update+0x71f/0xe10 security/keys/key.c:930
>  key_create_or_update+0x42/0x60 security/keys/key.c:1018
>  __do_sys_add_key+0x29c/0x460 security/keys/keyctl.c:134
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> Freed by task 46:
>  kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
>  kasan_save_track+0x14/0x30 mm/kasan/common.c:68
>  kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:579
>  poison_slab_object mm/kasan/common.c:247 [inline]
>  __kasan_slab_free+0x51/0x70 mm/kasan/common.c:264
>  kasan_slab_free include/linux/kasan.h:230 [inline]
>  slab_free_hook mm/slub.c:2342 [inline]
>  slab_free mm/slub.c:4579 [inline]
>  kmem_cache_free+0x152/0x4b0 mm/slub.c:4681
>  key_gc_unused_keys.constprop.0+0x134/0x480 security/keys/gc.c:167
>  key_garbage_collector+0x432/0x990 security/keys/gc.c:300
>  process_one_work+0x9c5/0x1ba0 kernel/workqueue.c:3229
>  process_scheduled_works kernel/workqueue.c:3310 [inline]
>  worker_thread+0x6c8/0xf00 kernel/workqueue.c:3391
>  kthread+0x2c1/0x3a0 kernel/kthread.c:389
>  ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
>  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
>
> The buggy address belongs to the object at ffff888079173a40
>  which belongs to the cache key_jar of size 336
> The buggy address is located 192 bytes inside of
>  freed 336-byte region [ffff888079173a40, ffff888079173b90)
>
> The buggy address belongs to the physical page:
> page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x79172
> head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
> flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
> page_type: f5(slab)
> raw: 00fff00000000040 ffff88801c2ba140 dead000000000122 0000000000000000
> raw: 0000000000000000 0000000080120012 00000001f5000000 0000000000000000
> head: 00fff00000000040 ffff88801c2ba140 dead000000000122 0000000000000000
> head: 0000000000000000 0000000080120012 00000001f5000000 0000000000000000
> head: 00fff00000000001 ffffea0001e45c81 ffffffffffffffff 0000000000000000
> head: 0000000000000002 0000000000000000 00000000ffffffff 0000000000000000
> page dumped because: kasan: bad access detected
> page_owner tracks the page as allocated
> page last allocated via order 1, migratetype Unmovable, gfp_mask
> 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC),
> pid 7134, tgid 7131 (syz-executor356), ts 90591707414, free_ts 84975549277
>  set_page_owner include/linux/page_owner.h:32 [inline]
>  post_alloc_hook+0x2d1/0x350 mm/page_alloc.c:1556
>  prep_new_page mm/page_alloc.c:1564 [inline]
>  get_page_from_freelist+0xfce/0x2f80 mm/page_alloc.c:3474
>  __alloc_pages_noprof+0x223/0x25a0 mm/page_alloc.c:4751
>  alloc_pages_mpol_noprof+0x2c9/0x610 mm/mempolicy.c:2265
>  alloc_slab_page mm/slub.c:2412 [inline]
>  allocate_slab mm/slub.c:2578 [inline]
>  new_slab+0x2c9/0x410 mm/slub.c:2631
>  ___slab_alloc+0xdac/0x1880 mm/slub.c:3818
>  __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3908
>  __slab_alloc_node mm/slub.c:3961 [inline]
>  slab_alloc_node mm/slub.c:4122 [inline]
>  kmem_cache_alloc_noprof+0x2a7/0x2f0 mm/slub.c:4141
>  key_alloc+0x3e3/0x13a0 security/keys/key.c:277
>  keyring_alloc+0x44/0xc0 security/keys/keyring.c:526
>  install_process_keyring_to_cred security/keys/process_keys.c:275 [inline]
>  install_process_keyring security/keys/process_keys.c:300 [inline]
>  lookup_user_key+0xa34/0x12f0 security/keys/process_keys.c:653
>  __do_sys_add_key+0x25a/0x460 security/keys/keyctl.c:126
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> page last free pid 6961 tgid 6958 stack trace:
>  reset_page_owner include/linux/page_owner.h:25 [inline]
>  free_pages_prepare mm/page_alloc.c:1127 [inline]
>  free_unref_page+0x661/0x1080 mm/page_alloc.c:2657
>  qlink_free mm/kasan/quarantine.c:163 [inline]
>  qlist_free_all+0x4e/0x120 mm/kasan/quarantine.c:179
>  kasan_quarantine_reduce+0x192/0x1e0 mm/kasan/quarantine.c:286
>  __kasan_slab_alloc+0x69/0x90 mm/kasan/common.c:329
>  kasan_slab_alloc include/linux/kasan.h:247 [inline]
>  slab_post_alloc_hook mm/slub.c:4085 [inline]
>  slab_alloc_node mm/slub.c:4134 [inline]
>  __kmalloc_cache_node_noprof+0x173/0x350 mm/slub.c:4303
>  kmalloc_node_noprof include/linux/slab.h:901 [inline]
>  alloc_user_cpus_ptr kernel/sched/sched.h:2614 [inline]
>  sched_setaffinity+0x252/0x430 kernel/sched/syscalls.c:1282
>  __do_sys_sched_setaffinity kernel/sched/syscalls.c:1331 [inline]
>  __se_sys_sched_setaffinity kernel/sched/syscalls.c:1320 [inline]
>  __x64_sys_sched_setaffinity+0x101/0x170 kernel/sched/syscalls.c:1320
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> Memory state around the buggy address:
>  ffff888079173a00: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
>  ffff888079173a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >ffff888079173b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>                    ^
>  ffff888079173b80: fb fb fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>  ffff888079173c00: fc fc fc fc fc fc fc fc fc fc fc fc 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.
>
> If the report is already addressed, let syzbot know by replying with:
> #syz fix: exact-commit-title
>
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.
>
> If you want to overwrite report's subsystems, reply with:
> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
>
> If the report is a duplicate of another one, reply with:
> #syz dup: exact-subject-of-another-report
>
> If you want to undo deduplication, reply with:
> #syz undup
>
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> .
>

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From ffe3a0a07e949f44404f430057fe82d8e73b2b61 Mon Sep 17 00:00:00 2001
From: Suraj Sonawane <surajsonawane0215@gmail.com>
Date: Tue, 19 Nov 2024 02:47:47 +0530
Subject: [PATCH] fix slab-after-free read

syz test

Signed-off-by: Suraj Sonawane <surajsonawane0215@gmail.com>
---
 security/keys/gc.c  |  2 ++
 security/keys/key.c | 16 +++++++++++++---
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/security/keys/gc.c b/security/keys/gc.c
index 7d687b096..9b19a972d 100644
--- a/security/keys/gc.c
+++ b/security/keys/gc.c
@@ -143,6 +143,7 @@ static noinline void key_gc_unused_keys(struct list_head *keys)
 
 		kdebug("- %u", key->serial);
 		key_check(key);
+		WRITE_ONCE(key->state, KEY_IS_DEAD);
 
 #ifdef CONFIG_KEY_NOTIFICATIONS
 		remove_watch_list(key->watchers, key->serial);
@@ -159,6 +160,7 @@ static noinline void key_gc_unused_keys(struct list_head *keys)
 		if (state != KEY_IS_UNINSTANTIATED)
 			atomic_dec(&key->user->nikeys);
 
+		smp_wmb();
 		key_user_put(key->user);
 		key_put_tag(key->domain_tag);
 		kfree(key->description);
diff --git a/security/keys/key.c b/security/keys/key.c
index 3d7d18501..5356da9d9 100644
--- a/security/keys/key.c
+++ b/security/keys/key.c
@@ -274,14 +274,22 @@ struct key *key_alloc(struct key_type *type, const char *desc,
 	}
 
 	/* allocate and initialise the key and its description */
-	key = kmem_cache_zalloc(key_jar, GFP_KERNEL);
+	key = kmem_cache_zalloc(key_jar, GFP_KERNEL | __GFP_ZERO);
 	if (!key)
 		goto no_memory_2;
 
 	key->index_key.desc_len = desclen;
 	key->index_key.description = kmemdup(desc, desclen + 1, GFP_KERNEL);
-	if (!key->index_key.description)
-		goto no_memory_3;
+
+	if (!key->index_key.description) {
+		kmem_cache_free(key_jar, key);
+		return ERR_PTR(-ENOMEM);
+	} else {
+		/* Ensure memory is correctly associated */
+		smp_wmb(); /* Memory barrier to ensure key is set before use */
+		key->state = KEY_IS_UNINSTANTIATED;
+	}
+
 	key->index_key.type = type;
 	key_set_index_key(&key->index_key);
 
@@ -651,6 +659,8 @@ void key_put(struct key *key)
 		if (refcount_dec_and_test(&key->usage)) {
 			unsigned long flags;
 
+			WRITE_ONCE(key->state, KEY_IS_DEAD);
+
 			/* deal with the user's key tracking and quota */
 			if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
 				spin_lock_irqsave(&key->user->lock, flags);
-- 
2.34.1