Re: [PATCH] crypto: sun8i-ce - Fix use after free in unprepare.

On 24-02-27 00:53, Andrey Skvortsov wrote:

sun8i_ce_cipher_unprepare should be called before
crypto_finalize_skcipher_request, because client callbacks may
immediately free memory, that isn't needed anymore. But it will be
used by unprepare after free. Before removing prepare/unprepare
callbacks it was handled by crypto engine in crypto_finalize_request.

And potentially rk3288_crypto driver is affected by the similar
problem.

https://elixir.bootlin.com/linux/v6.8-rc6/source/drivers/crypto/rockchip/rk3288_crypto_ahash.c#L339

Usually that results in a pointer dereference problem during a in
crypto selftest.
 Unable to handle kernel NULL pointer dereference at
                                      virtual address 0000000000000030
 Mem abort info:
   ESR = 0x0000000096000004
   EC = 0x25: DABT (current EL), IL = 32 bits
   SET = 0, FnV = 0
   EA = 0, S1PTW = 0
   FSC = 0x04: level 0 translation fault
 Data abort info:
   ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000
   CM = 0, WnR = 0, TnD = 0, TagAccess = 0
   GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
 user pgtable: 4k pages, 48-bit VAs, pgdp=000000004716d000
 [0000000000000030] pgd=0000000000000000, p4d=0000000000000000
 Internal error: Oops: 0000000096000004 [#1] SMP

This problem is detected by KASAN as well.
 ==================================================================
 BUG: KASAN: slab-use-after-free in sun8i_ce_cipher_do_one+0x6e8/0xf80 [sun8i_ce]
 Read of size 8 at addr ffff00000dcdc040 by task 1c15000.crypto-/373

 Hardware name: Pine64 PinePhone (1.2) (DT)
 Call trace:
  dump_backtrace+0x9c/0x128
  show_stack+0x20/0x38
  dump_stack_lvl+0x48/0x60
  print_report+0xf8/0x5d8
  kasan_report+0x90/0xd0
  __asan_load8+0x9c/0xc0
  sun8i_ce_cipher_do_one+0x6e8/0xf80 [sun8i_ce]
  crypto_pump_work+0x354/0x620 [crypto_engine]
  kthread_worker_fn+0x244/0x498
  kthread+0x168/0x178
  ret_from_fork+0x10/0x20

 Allocated by task 379:
  kasan_save_stack+0x3c/0x68
  kasan_set_track+0x2c/0x40
  kasan_save_alloc_info+0x24/0x38
  __kasan_kmalloc+0xd4/0xd8
  __kmalloc+0x74/0x1d0
  alg_test_skcipher+0x90/0x1f0
  alg_test+0x24c/0x830
  cryptomgr_test+0x38/0x60
  kthread+0x168/0x178
  ret_from_fork+0x10/0x20

 Freed by task 379:
  kasan_save_stack+0x3c/0x68
  kasan_set_track+0x2c/0x40
  kasan_save_free_info+0x38/0x60
  __kasan_slab_free+0x100/0x170
  slab_free_freelist_hook+0xd4/0x1e8
  __kmem_cache_free+0x15c/0x290
  kfree+0x74/0x100
  kfree_sensitive+0x80/0xb0
  alg_test_skcipher+0x12c/0x1f0
  alg_test+0x24c/0x830
  cryptomgr_test+0x38/0x60
  kthread+0x168/0x178
  ret_from_fork+0x10/0x20

 The buggy address belongs to the object at ffff00000dcdc000
  which belongs to the cache kmalloc-256 of size 256
 The buggy address is located 64 bytes inside of
  freed 256-byte region [ffff00000dcdc000, ffff00000dcdc100)

Signed-off-by: Andrey Skvortsov <redacted>
Fixes: 4136212ab18e ("crypto: sun8i-ce - Remove prepare/unprepare request")

-- 
Best regards,
Andrey Skvortsov

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