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Message-Id: <1456482100-4667-103-git-send-email-luis.henriques@canonical.com> Date: Fri, 26 Feb 2016 10:21:13 +0000 From: Luis Henriques <luis.henriques@...onical.com> To: linux-kernel@...r.kernel.org, stable@...r.kernel.org, kernel-team@...ts.ubuntu.com Cc: Mathias Krause <minipli@...glemail.com>, Steffen Klassert <steffen.klassert@...unet.com>, PaX Team <pageexec@...email.hu>, Herbert Xu <herbert@...dor.apana.org.au>, Luis Henriques <luis.henriques@...onical.com> Subject: [PATCH 3.16.y-ckt 102/129] crypto: user - lock crypto_alg_list on alg dump 3.16.7-ckt25 -stable review patch. If anyone has any objections, please let me know. ---8<------------------------------------------------------------ From: Mathias Krause <minipli@...glemail.com> commit 63e41ebc6630f39422d87f8a4bade1e793f37a01 upstream. We miss to take the crypto_alg_sem semaphore when traversing the crypto_alg_list for CRYPTO_MSG_GETALG dumps. This allows a race with crypto_unregister_alg() removing algorithms from the list while we're still traversing it, thereby leading to a use-after-free as show below: [ 3482.071639] general protection fault: 0000 [#1] SMP [ 3482.075639] Modules linked in: aes_x86_64 glue_helper lrw ablk_helper cryptd gf128mul ipv6 pcspkr serio_raw virtio_net microcode virtio_pci virtio_ring virtio sr_mod cdrom [last unloaded: aesni_intel] [ 3482.075639] CPU: 1 PID: 11065 Comm: crconf Not tainted 4.3.4-grsec+ #126 [ 3482.075639] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20140531_083030-gandalf 04/01/2014 [ 3482.075639] task: ffff88001cd41a40 ti: ffff88001cd422c8 task.ti: ffff88001cd422c8 [ 3482.075639] RIP: 0010:[<ffffffff93722bd3>] [<ffffffff93722bd3>] strncpy+0x13/0x30 [ 3482.075639] RSP: 0018:ffff88001f713b60 EFLAGS: 00010202 [ 3482.075639] RAX: ffff88001f6c4430 RBX: ffff88001f6c43a0 RCX: ffff88001f6c4430 [ 3482.075639] RDX: 0000000000000040 RSI: fefefefefefeff16 RDI: ffff88001f6c4430 [ 3482.075639] RBP: ffff88001f713b60 R08: ffff88001f6c4470 R09: ffff88001f6c4480 [ 3482.075639] R10: 0000000000000002 R11: 0000000000000246 R12: ffff88001ce2aa28 [ 3482.075639] R13: ffff880000093700 R14: ffff88001f5e4bf8 R15: 0000000000003b20 [ 3482.075639] FS: 0000033826fa2700(0000) GS:ffff88001e900000(0000) knlGS:0000000000000000 [ 3482.075639] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 3482.075639] CR2: ffffffffff600400 CR3: 00000000139ec000 CR4: 00000000001606f0 [ 3482.075639] Stack: [ 3482.075639] ffff88001f713bd8 ffffffff936ccd00 ffff88001e5c4200 ffff880000093700 [ 3482.075639] ffff88001f713bd0 ffffffff938ef4bf 0000000000000000 0000000000003b20 [ 3482.075639] ffff88001f5e4bf8 ffff88001f5e4848 0000000000000000 0000000000003b20 [ 3482.075639] Call Trace: [ 3482.075639] [<ffffffff936ccd00>] crypto_report_alg+0xc0/0x3e0 [ 3482.075639] [<ffffffff938ef4bf>] ? __alloc_skb+0x16f/0x300 [ 3482.075639] [<ffffffff936cd08a>] crypto_dump_report+0x6a/0x90 [ 3482.075639] [<ffffffff93935707>] netlink_dump+0x147/0x2e0 [ 3482.075639] [<ffffffff93935f99>] __netlink_dump_start+0x159/0x190 [ 3482.075639] [<ffffffff936ccb13>] crypto_user_rcv_msg+0xc3/0x130 [ 3482.075639] [<ffffffff936cd020>] ? crypto_report_alg+0x3e0/0x3e0 [ 3482.075639] [<ffffffff936cc4b0>] ? alg_test_crc32c+0x120/0x120 [ 3482.075639] [<ffffffff93933145>] ? __netlink_lookup+0xd5/0x120 [ 3482.075639] [<ffffffff936cca50>] ? crypto_add_alg+0x1d0/0x1d0 [ 3482.075639] [<ffffffff93938141>] netlink_rcv_skb+0xe1/0x130 [ 3482.075639] [<ffffffff936cc4f8>] crypto_netlink_rcv+0x28/0x40 [ 3482.075639] [<ffffffff939375a8>] netlink_unicast+0x108/0x180 [ 3482.075639] [<ffffffff93937c21>] netlink_sendmsg+0x541/0x770 [ 3482.075639] [<ffffffff938e31e1>] sock_sendmsg+0x21/0x40 [ 3482.075639] [<ffffffff938e4763>] SyS_sendto+0xf3/0x130 [ 3482.075639] [<ffffffff93444203>] ? bad_area_nosemaphore+0x13/0x20 [ 3482.075639] [<ffffffff93444470>] ? __do_page_fault+0x80/0x3a0 [ 3482.075639] [<ffffffff939d80cb>] entry_SYSCALL_64_fastpath+0x12/0x6e [ 3482.075639] Code: 88 4a ff 75 ed 5d 48 0f ba 2c 24 3f c3 66 66 2e 0f 1f 84 00 00 00 00 00 55 48 85 d2 48 89 f8 48 89 f9 4c 8d 04 17 48 89 e5 74 15 <0f> b6 16 80 fa 01 88 11 48 83 de ff 48 83 c1 01 4c 39 c1 75 eb [ 3482.075639] RIP [<ffffffff93722bd3>] strncpy+0x13/0x30 To trigger the race run the following loops simultaneously for a while: $ while : ; do modprobe aesni-intel; rmmod aesni-intel; done $ while : ; do crconf show all > /dev/null; done Fix the race by taking the crypto_alg_sem read lock, thereby preventing crypto_unregister_alg() from modifying the algorithm list during the dump. This bug has been detected by the PaX memory sanitize feature. Signed-off-by: Mathias Krause <minipli@...glemail.com> Cc: Steffen Klassert <steffen.klassert@...unet.com> Cc: PaX Team <pageexec@...email.hu> Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au> Signed-off-by: Luis Henriques <luis.henriques@...onical.com> --- crypto/crypto_user.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/crypto/crypto_user.c b/crypto/crypto_user.c index c90af2537d24..c571d85cfad7 100644 --- a/crypto/crypto_user.c +++ b/crypto/crypto_user.c @@ -483,6 +483,7 @@ static int crypto_user_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh) if (link->dump == NULL) return -EINVAL; + down_read(&crypto_alg_sem); list_for_each_entry(alg, &crypto_alg_list, cra_list) dump_alloc += CRYPTO_REPORT_MAXSIZE; @@ -492,8 +493,11 @@ static int crypto_user_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh) .done = link->done, .min_dump_alloc = dump_alloc, }; - return netlink_dump_start(crypto_nlsk, skb, nlh, &c); + err = netlink_dump_start(crypto_nlsk, skb, nlh, &c); } + up_read(&crypto_alg_sem); + + return err; } err = nlmsg_parse(nlh, crypto_msg_min[type], attrs, CRYPTOCFGA_MAX,
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