linux-kernel - Re: KASAN: slab-out-of-bounds Write in sha3

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Date:   Tue, 16 Jan 2018 22:33:31 -0800
From:   Eric Biggers <ebiggers3@...il.com>
To:     syzbot 
        <bot+80f661b525da04e7baaef60ee883f18be36f3942@...kaller.appspotmail.com>
Cc:     davem@...emloft.net, herbert@...dor.apana.org.au,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        keyrings@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: KASAN: slab-out-of-bounds Write in sha3_update (2)

On Fri, Dec 22, 2017 at 11:22:38AM -0600, Eric Biggers wrote:
> [+Cc keyrings@...r.kernel.org]
> 
> On Fri, Dec 22, 2017 at 07:55:01AM -0800, syzbot wrote:
> > Hello,
> > 
> > syzkaller hit the following crash on
> > 9035a8961b504d0997369509ab8c6b1f0a4ee33d
> > git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master
> > compiler: gcc (GCC) 7.1.1 20170620
> > .config is attached
> > Raw console output is attached.
> > C reproducer is attached
> > syzkaller reproducer is attached. See https://goo.gl/kgGztJ
> > for information about syzkaller reproducers
> > 
> > 
> > audit: type=1400 audit(1513919078.260:7): avc:  denied  { map } for
> > pid=3152 comm="syzkaller717822" path="/root/syzkaller717822551" dev="sda1"
> > ino=16481 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023
> > tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1
> > ==================================================================
> > BUG: KASAN: slab-out-of-bounds in memcpy include/linux/string.h:344 [inline]
> > BUG: KASAN: slab-out-of-bounds in sha3_update+0xdf/0x2e0
> > crypto/sha3_generic.c:161
> > Write of size 192 at addr ffff8801cf0e3b3c by task syzkaller717822/3152
> > 
> > CPU: 0 PID: 3152 Comm: syzkaller717822 Not tainted 4.15.0-rc4+ #232
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> > Google 01/01/2011
> > Call Trace:
> >  __dump_stack lib/dump_stack.c:17 [inline]
> >  dump_stack+0x194/0x257 lib/dump_stack.c:53
> >  print_address_description+0x73/0x250 mm/kasan/report.c:252
> >  kasan_report_error mm/kasan/report.c:351 [inline]
> >  kasan_report+0x25b/0x340 mm/kasan/report.c:409
> >  check_memory_region_inline mm/kasan/kasan.c:260 [inline]
> >  check_memory_region+0x137/0x190 mm/kasan/kasan.c:267
> >  memcpy+0x37/0x50 mm/kasan/kasan.c:303
> >  memcpy include/linux/string.h:344 [inline]
> >  sha3_update+0xdf/0x2e0 crypto/sha3_generic.c:161
> >  crypto_shash_update+0xda/0x240 crypto/shash.c:110
> >  hmac_update+0x7e/0xa0 crypto/hmac.c:122
> >  crypto_shash_update+0xda/0x240 crypto/shash.c:110
> >  kdf_ctr security/keys/dh.c:181 [inline]
> >  keyctl_dh_compute_kdf security/keys/dh.c:226 [inline]
> >  __keyctl_dh_compute+0x160f/0x1990 security/keys/dh.c:398
> >  keyctl_dh_compute+0xac/0xf3 security/keys/dh.c:434
> >  SYSC_keyctl security/keys/keyctl.c:1741 [inline]
> >  SyS_keyctl+0x72/0x2c0 security/keys/keyctl.c:1637
> >  entry_SYSCALL_64_fastpath+0x1f/0x96
> > RIP: 0033:0x43feb9
> > RSP: 002b:00007ffd3aef51a8 EFLAGS: 00000217 ORIG_RAX: 00000000000000fa
> > RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 000000000043feb9
> > RDX: 0000000020c2cfff RSI: 00000000204c8ff4 RDI: 0000000000000017
> > RBP: 00000000006ca018 R08: 00000000208e6fd4 R09: 0000000000000000
> > R10: 0000000000000001 R11: 0000000000000217 R12: 0000000000401820
> > R13: 00000000004018b0 R14: 0000000000000000 R15: 0000000000000000
> > 
> > Allocated by task 3152:
> >  save_stack+0x43/0xd0 mm/kasan/kasan.c:447
> >  set_track mm/kasan/kasan.c:459 [inline]
> >  kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
> >  __do_kmalloc mm/slab.c:3708 [inline]
> >  __kmalloc+0x162/0x760 mm/slab.c:3717
> >  kmalloc include/linux/slab.h:504 [inline]
> >  kdf_alloc security/keys/dh.c:111 [inline]
> >  __keyctl_dh_compute+0x2b0/0x1990 security/keys/dh.c:288
> >  keyctl_dh_compute+0xac/0xf3 security/keys/dh.c:434
> >  SYSC_keyctl security/keys/keyctl.c:1741 [inline]
> >  SyS_keyctl+0x72/0x2c0 security/keys/keyctl.c:1637
> >  entry_SYSCALL_64_fastpath+0x1f/0x96
> > 
> > Freed by task 1637:
> >  save_stack+0x43/0xd0 mm/kasan/kasan.c:447
> >  set_track mm/kasan/kasan.c:459 [inline]
> >  kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
> >  __cache_free mm/slab.c:3488 [inline]
> >  kfree+0xd6/0x260 mm/slab.c:3803
> >  kernfs_fop_release+0x13f/0x180 fs/kernfs/file.c:783
> >  __fput+0x327/0x7e0 fs/file_table.c:210
> >  ____fput+0x15/0x20 fs/file_table.c:244
> >  task_work_run+0x199/0x270 kernel/task_work.c:113
> >  tracehook_notify_resume include/linux/tracehook.h:191 [inline]
> >  exit_to_usermode_loop+0x296/0x310 arch/x86/entry/common.c:162
> >  prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
> >  syscall_return_slowpath+0x490/0x550 arch/x86/entry/common.c:264
> >  entry_SYSCALL_64_fastpath+0x94/0x96
> > 
> 
> The problem is that KEYCTL_DH_COMPUTE allows the user to request and use any
> hash algorithm as an unkeyed hash without checking whether it is in fact
> unkeyed.
> 
> We could fix this by checking for !crypto_shash_alg_has_setkey() after
> allocating the hash, but now I'd really like to solve this for all users by
> having crypto_[as]hash_init() and crypto_[as]hash_digest() automatically return
> -ENOKEY if a key is needed and one hasn't been set.  That would also have solved
> the bug I fixed specifically for HMAC by "crypto: hmac - require that the
> underlying hash algorithm is unkeyed".
> 
> Eric

Fixed in cryptodev/master by:

#syz fix: crypto: hash - prevent using keyed hashes without setting key