• Eric Biggers's avatar
    KEYS: fix freeing uninitialized memory in key_update() · 45771cd7
    Eric Biggers authored
    commit 63a0b050 upstream.
    
    key_update() freed the key_preparsed_payload even if it was not
    initialized first.  This would cause a crash if userspace called
    keyctl_update() on a key with type like "asymmetric" that has a
    ->preparse() method but not an ->update() method.  Possibly it could
    even be triggered for other key types by racing with keyctl_setperm() to
    make the KEY_NEED_WRITE check fail (the permission was already checked,
    so normally it wouldn't fail there).
    
    Reproducer with key type "asymmetric", given a valid cert.der:
    
    keyctl new_session
    keyid=$(keyctl padd asymmetric desc @s < cert.der)
    keyctl setperm $keyid 0x3f000000
    keyctl update $keyid data
    
    [  150.686666] BUG: unable to handle kernel NULL pointer dereference at 0000000000000001
    [  150.687601] IP: asymmetric_key_free_kids+0x12/0x30
    [  150.688139] PGD 38a3d067
    [  150.688141] PUD 3b3de067
    [  150.688447] PMD 0
    [  150.688745]
    [  150.689160] Oops: 0000 [#1] SMP
    [  150.689455] Modules linked in:
    [  150.689769] CPU: 1 PID: 2478 Comm: keyctl Not tainted 4.11.0-rc4-xfstests-00187-ga9f6b6b8 #742
    [  150.690916] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-20170228_101828-anatol 04/01/2014
    [  150.692199] task: ffff88003b30c480 task.stack: ffffc90000350000
    [  150.692952] RIP: 0010:asymmetric_key_free_kids+0x12/0x30
    [  150.693556] RSP: 0018:ffffc90000353e58 EFLAGS: 00010202
    [  150.694142] RAX: 0000000000000000 RBX: 0000000000000001 RCX: 0000000000000004
    [  150.694845] RDX: ffffffff81ee3920 RSI: ffff88003d4b0700 RDI: 0000000000000001
    [  150.697569] RBP: ffffc90000353e60 R08: ffff88003d5d2140 R09: 0000000000000000
    [  150.702483] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000001
    [  150.707393] R13: 0000000000000004 R14: ffff880038a4d2d8 R15: 000000000040411f
    [  150.709720] FS:  00007fcbcee35700(0000) GS:ffff88003fd00000(0000) knlGS:0000000000000000
    [  150.711504] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    [  150.712733] CR2: 0000000000000001 CR3: 0000000039eab000 CR4: 00000000003406e0
    [  150.714487] Call Trace:
    [  150.714975]  asymmetric_key_free_preparse+0x2f/0x40
    [  150.715907]  key_update+0xf7/0x140
    [  150.716560]  ? key_default_cmp+0x20/0x20
    [  150.717319]  keyctl_update_key+0xb0/0xe0
    [  150.718066]  SyS_keyctl+0x109/0x130
    [  150.718663]  entry_SYSCALL_64_fastpath+0x1f/0xc2
    [  150.719440] RIP: 0033:0x7fcbce75ff19
    [  150.719926] RSP: 002b:00007ffd5d167088 EFLAGS: 00000206 ORIG_RAX: 00000000000000fa
    [  150.720918] RAX: ffffffffffffffda RBX: 0000000000404d80 RCX: 00007fcbce75ff19
    [  150.721874] RDX: 00007ffd5d16785e RSI: 000000002866cd36 RDI: 0000000000000002
    [  150.722827] RBP: 0000000000000006 R08: 000000002866cd36 R09: 00007ffd5d16785e
    [  150.723781] R10: 0000000000000004 R11: 0000000000000206 R12: 0000000000404d80
    [  150.724650] R13: 00007ffd5d16784d R14: 00007ffd5d167238 R15: 000000000040411f
    [  150.725447] Code: 83 c4 08 31 c0 5b 41 5c 41 5d 41 5e 41 5f 5d c3 66 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 85 ff 74 23 55 48 89 e5 53 48 89 fb <48> 8b 3f e8 06 21 c5 ff 48 8b 7b 08 e8 fd 20 c5 ff 48 89 df e8
    [  150.727489] RIP: asymmetric_key_free_kids+0x12/0x30 RSP: ffffc90000353e58
    [  150.728117] CR2: 0000000000000001
    [  150.728430] ---[ end trace f7f8fe1da2d5ae8d ]---
    
    Fixes: 4d8c0250 ("KEYS: Call ->free_preparse() even after ->preparse() returns an error")
    Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
    Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
    Signed-off-by: default avatarJames Morris <james.l.morris@oracle.com>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    45771cd7
key.c 29.4 KB