[BUG] crypto: virtio - KASAN slab-use-after-free in virtio_crypto_skcipher_encrypt

[Shuangpeng Bai <shuangpeng.kernel@gmail.com>]

Hi,

I hit the following KASAN report while testing current upstream kernel.

The issue was reproduced by queuing an AF_ALG skcipher request backed by
virtio-crypto, unbinding virtio0 from the virtio_crypto driver, and then
receiving from the old AF_ALG op fd.

KASAN: slab-use-after-free in virtio_crypto_skcipher_encrypt

I reproduced this on commit: e8c2f9fdadee7cbc75134dc463c1e0d856d6e5c7 (May 25 2026)

The reproducer and .config files are here.
https://gist.github.com/shuangpengbai/f6117a0883dd574f02288ca812bb7d65

I'm happy to test debug patches or provide additional information.

Reported-by: Shuangpeng Bai <shuangpeng.kernel@gmail.com>

[   54.367992][ T8332] BUG: KASAN: slab-use-after-free in virtio_crypto_skcipher_encrypt (drivers/crypto/virtio/virtio_crypto_skcipher_algs.c:473)
[   54.369596][ T8332] Read of size 8 at addr ffff888124a47010 by task virtio_crypto_a/8332
[   54.370922][ T8332]
[   54.371171][ T8332] Tainted: [W]=WARN
[   54.371172][ T8332] Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[   54.371175][ T8332] Call Trace:
[   54.371179][ T8332]  <TASK>
[   54.371181][ T8332]  dump_stack_lvl (lib/dump_stack.c:94 lib/dump_stack.c:120)
[   54.371188][ T8332]  print_report (mm/kasan/report.c:378 mm/kasan/report.c:482)
[   54.371202][ T8332]  kasan_report (mm/kasan/report.c:595)
[   54.371213][ T8332]  virtio_crypto_skcipher_encrypt (drivers/crypto/virtio/virtio_crypto_skcipher_algs.c:473)
[   54.371216][ T8332]  skcipher_recvmsg (crypto/algif_skcipher.c:203 crypto/algif_skcipher.c:226)
[   54.371249][ T8332]  sock_recvmsg (net/socket.c:1137 net/socket.c:1159)
[   54.371253][ T8332]  __sys_recvfrom (net/socket.c:2315)
[   54.371273][ T8332]  __x64_sys_recvfrom (net/socket.c:2330 net/socket.c:2326 net/socket.c:2326)
[   54.371277][ T8332]  do_syscall_64 (arch/x86/entry/syscall_64.c:63 arch/x86/entry/syscall_64.c:94)
[   54.371281][ T8332]  entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)
[   54.371285][ T8332] RIP: 0033:0x7f3c6caaac2c
[   54.371289][ T8332] Code: 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 41 89 ca 64 8b 04 25 18 00 00 00 85 c0 75 19 45 31 c9 45 31 c0 b8 2d 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 64 c3 0f 1f 00 55 48 83 ec 20 48 89 54 24 10
[   54.371292][ T8332] RSP: 002b:00007ffed3785308 EFLAGS: 00000246 ORIG_RAX: 000000000000002d
[   54.371297][ T8332] RAX: ffffffffffffffda RBX: 0000000000000064 RCX: 00007f3c6caaac2c
[   54.371299][ T8332] RDX: 0000000000000040 RSI: 00007ffed37853a0 RDI: 0000000000000004
[   54.371301][ T8332] RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000000
[   54.371303][ T8332] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000004
[   54.371305][ T8332] R13: 00007ffed37853a0 R14: 0000558cc9904118 R15: 0000000000000000
[   54.371309][ T8332]  </TASK>
[   54.371311][ T8332]
[   54.394932][ T8332] Freed by task 8332 on cpu 0 at 54.364772s:
[   54.395528][ T8332]  kasan_save_track (mm/kasan/common.c:57 mm/kasan/common.c:78)
[   54.395997][ T8332]  kasan_save_free_info (mm/kasan/generic.c:584)
[   54.396501][ T8332]  __kasan_slab_free (mm/kasan/common.c:253 mm/kasan/common.c:285)
[   54.396983][ T8332]  kfree (include/linux/kasan.h:235 mm/slub.c:2689 mm/slub.c:6251 mm/slub.c:6566)
[   54.397378][ T8332]  virtio_dev_remove (drivers/virtio/virtio.c:375)
[   54.397869][ T8332]  device_release_driver_internal (drivers/base/dd.c:619 drivers/base/dd.c:1352 drivers/base/dd.c:1375)
[   54.398475][ T8332]  unbind_store (drivers/base/bus.c:244)
[   54.398944][ T8332]  kernfs_fop_write_iter (fs/kernfs/file.c:352)
[   54.399476][ T8332]  vfs_write (fs/read_write.c:595 fs/read_write.c:688)
[   54.399915][ T8332]  ksys_write (fs/read_write.c:740)
[   54.400349][ T8332]  do_syscall_64 (arch/x86/entry/syscall_64.c:63 arch/x86/entry/syscall_64.c:94)
[   54.400818][ T8332]  entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)
[   54.401406][ T8332]
[   54.401650][ T8332] The buggy address belongs to the object at ffff888124a47000
[   54.401650][ T8332]  which belongs to the cache kmalloc-192 of size 192
[   54.403038][ T8332] The buggy address is located 16 bytes inside of
[   54.403038][ T8332]  freed 192-byte region [ffff888124a47000, ffff888124a470c0)
[   54.404385][ T8332]


Best,
Shuangpeng