KASAN: slab-use-after-free Read in key_put

syzbot syzbot 4 participants 8 messages Nov 18, 2024 – Mar 19, 2025

Subsystems (2)

Security (LSM) Keys/keyrings

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author syzbot

2024-11-18 16:27 UTC #0 lore raw

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 [email protected]

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 [email protected].

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

Suraj Sonawane

2024-11-18 21:27 UTC #1 lore raw

#syz test

Quoted 202 lines · syzbot

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 [email protected]

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

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 [email protected].

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

Quoted 9 lines

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.

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

syz test

Signed-off-by Suraj Sonawane <[email protected]>

---
 security/keys/gc.c  |  2 ++
 security/keys/key.c | 16 +++++++++++++---
 2 files changed, 15 insertions(+), 3 deletions(-)

security/keys/gc.c +2 -0

index 7d687b096..9b19a972d 100644
@@ -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);

security/keys/key.c +13 -3

index 3d7d18501..5356da9d9 100644
@@ -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);

Signature · 1 line

2.34.1

syzbot

author syzbot

2024-11-18 21:37 UTC #2 lore raw

syzbot tried to test the proposed patch but the build/boot failed:

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

security/keys/gc.c:146:40: error: 'KEY_IS_DEAD' undeclared (first use in this function); did you mean 'KEY_USR_READ'?

Tested on:

commit:         9fb2cfa4 Merge tag 'pull-ufs' of git://git.kernel.org/..
git tree:       upstream
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
patch:          https://syzkaller.appspot.com/x/patch.diff?x=1781eac0580000

syzbot

author syzbot

2024-11-19 10:36 UTC #3 lore raw

In reply to syzbot

syzbot has bisected this issue to:

commit 9578e327b2b4935a25d49e3891b8fcca9b6c10c6

Author: Luis Henriques <[email protected]>
Date:   Tue Jan 30 10:13:44 2024 +0000

keys: update key quotas in key_put()

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=10821bf7980000
start commit:   adc218676eef Linux 6.12
git tree:       upstream
final oops:     https://syzkaller.appspot.com/x/report.txt?x=12821bf7980000
console output: https://syzkaller.appspot.com/x/log.txt?x=14821bf7980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=55f8591b98dd132
dashboard link: https://syzkaller.appspot.com/bug?extid=6105ffc1ded71d194d6d
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12dbbb5f980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=11c672e8580000

Reported-by [email protected]

Fixes 9578e327b2b4 ("keys: update key quotas in key_put()")

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

Hillf Danton

2024-11-20 10:43 UTC #4 lore raw

In reply to syzbot

On Mon, 18 Nov 2024 08:27:24 -0800

Quoted 5 lines

syzbot found the following issue on:

HEAD commit:    adc218676eef Linux 6.12
git tree:       upstream
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=11c672e8580000

#syz test

security/keys/key.c +14 -5

@@ -645,21 +645,30 @@ EXPORT_SYMBOL(key_reject_and_link);
  */
 void key_put(struct key *key)
 {
+	int quota_flag;
+	unsigned short len;
+	struct key_user *user;
+
 	if (key) {
 		key_check(key);
 
+		quota_flag = test_bit(KEY_FLAG_IN_QUOTA, &key->flags);
+		len = key->quotalen;
+		user = key->user;
+		refcount_inc(&user->usage);
 		if (refcount_dec_and_test(&key->usage)) {
 			unsigned long flags;
 
 			/* 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);
-				key->user->qnkeys--;
-				key->user->qnbytes -= key->quotalen;
-				spin_unlock_irqrestore(&key->user->lock, flags);
+			if (quota_flag) {
+				spin_lock_irqsave(&user->lock, flags);
+				user->qnkeys--;
+				user->qnbytes -= len;
+				spin_unlock_irqrestore(&user->lock, flags);
 			}
 			schedule_work(&key_gc_work);
 		}
+		key_user_put(user);
 	}
 }
 EXPORT_SYMBOL(key_put);

syzbot

author syzbot Tested-by

2024-11-20 11:15 UTC #5 lore raw

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by [email protected]

Tested-by [email protected]

Tested on:

commit:         bf9aa14f Merge tag 'timers-core-2024-11-18' of git://g..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16a2e930580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8b2ddebc25a60ddb
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
patch:          https://syzkaller.appspot.com/x/patch.diff?x=12ad4ae8580000

Note: testing is done by a robot and is best-effort only.

David Howells

maintainer

2025-03-19 15:20 UTC #6 lore raw

In reply to syzbot

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

commit 91286ccf56bb5030c0c84b11684f06142f50e681

Author: David Howells <[email protected]>
Date:   Tue Mar 18 09:54:54 2025 +0000

keys: Fix UAF in key_put()

Once a key's reference count has been reduced to 0, the garbage collector thread may destroy it at any time and so key_put() is not allowed to touch the key after that point. The most key_put() is normally allowed to do is to touch key_gc_work as that's a static global variable.

However, in an effort to speed up the reclamation of quota, this is now done in key_put() once the key's usage is reduced to 0 - but now the code is looking at the key after the deadline, which is forbidden.

Fix this by using a flag to indicate that a key can be gc'd now rather than looking at the key's refcount in the garbage collector.

Fixes 9578e327b2b4 ("keys: update key quotas in key_put()")

Reported-by [email protected]

Signed-off-by David Howells <[email protected]>

cc Jarkko Sakkinen <[email protected]>

cc Oleg Nesterov <[email protected]>

cc Kees Cook <[email protected]>

cc Hillf Danton <[email protected]>,

cc [email protected]

Cc [email protected] # v6.10+

include/linux/key.h +1 -0

index 074dca3222b9..ba05de8579ec 100644
@@ -236,6 +236,7 @@ struct key {
 #define KEY_FLAG_ROOT_CAN_INVAL	7	/* set if key can be invalidated by root without permission */
 #define KEY_FLAG_KEEP		8	/* set if key should not be removed */
 #define KEY_FLAG_UID_KEYRING	9	/* set if key is a user or user session keyring */
+#define KEY_FLAG_FINAL_PUT	10	/* set if final put has happened on key */
 
 	/* the key type and key description string
 	 * - the desc is used to match a key against search criteria

security/keys/gc.c +3 -1

index 7d687b0962b1..f27223ea4578 100644
@@ -218,8 +218,10 @@ static void key_garbage_collector(struct work_struct *work)
 		key = rb_entry(cursor, struct key, serial_node);
 		cursor = rb_next(cursor);
 
-		if (refcount_read(&key->usage) == 0)
+		if (test_bit(KEY_FLAG_FINAL_PUT, &key->flags)) {
+			smp_mb(); /* Clobber key->user after FINAL_PUT seen. */
 			goto found_unreferenced_key;
+		}
 
 		if (unlikely(gc_state & KEY_GC_REAPING_DEAD_1)) {
 			if (key->type == key_gc_dead_keytype) {

security/keys/key.c +2 -0

index 3d7d185019d3..7198cd2ac3a3 100644
@@ -658,6 +658,8 @@ void key_put(struct key *key)
 				key->user->qnbytes -= key->quotalen;
 				spin_unlock_irqrestore(&key->user->lock, flags);
 			}
+			smp_mb(); /* key->user before FINAL_PUT set. */
+			set_bit(KEY_FLAG_FINAL_PUT, &key->flags);
 			schedule_work(&key_gc_work);
 		}
 	}

syzbot

author syzbot Tested-by

2025-03-19 15:49 UTC #7 lore raw

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by [email protected]

Tested-by [email protected]

Tested on:

commit:         81e4f8d6 Merge tag 'pmdomain-v6.14-rc4' of git://git.k..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1216744c580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=14213ea05709bce7
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
patch:          https://syzkaller.appspot.com/x/patch.diff?x=16bb93b0580000

Note: testing is done by a robot and is best-effort only.