From de4788d85edff1a4411eb8cfcefb61f9ba655b89 Mon Sep 17 00:00:00 2001 From: Mathias Krause Date: Mon, 1 Feb 2016 14:27:30 +0100 Subject: crypto: user - lock crypto_alg_list on alg dump 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:[] [] 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] [] crypto_report_alg+0xc0/0x3e0 [ 3482.075639] [] ? __alloc_skb+0x16f/0x300 [ 3482.075639] [] crypto_dump_report+0x6a/0x90 [ 3482.075639] [] netlink_dump+0x147/0x2e0 [ 3482.075639] [] __netlink_dump_start+0x159/0x190 [ 3482.075639] [] crypto_user_rcv_msg+0xc3/0x130 [ 3482.075639] [] ? crypto_report_alg+0x3e0/0x3e0 [ 3482.075639] [] ? alg_test_crc32c+0x120/0x120 [ 3482.075639] [] ? __netlink_lookup+0xd5/0x120 [ 3482.075639] [] ? crypto_add_alg+0x1d0/0x1d0 [ 3482.075639] [] netlink_rcv_skb+0xe1/0x130 [ 3482.075639] [] crypto_netlink_rcv+0x28/0x40 [ 3482.075639] [] netlink_unicast+0x108/0x180 [ 3482.075639] [] netlink_sendmsg+0x541/0x770 [ 3482.075639] [] sock_sendmsg+0x21/0x40 [ 3482.075639] [] SyS_sendto+0xf3/0x130 [ 3482.075639] [] ? bad_area_nosemaphore+0x13/0x20 [ 3482.075639] [] ? __do_page_fault+0x80/0x3a0 [ 3482.075639] [] 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 [] 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. Cc: stable@vger.kernel.org Signed-off-by: Mathias Krause Cc: Steffen Klassert Cc: PaX Team Signed-off-by: Herbert Xu --- 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 237f3795..43fe85f2 100644 --- a/crypto/crypto_user.c +++ b/crypto/crypto_user.c @@ -499,6 +499,7 @@ 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; @@ -508,8 +509,11 @@ 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, -- cgit v1.2.3 From 5290ac69bd1d735d4cb02b518c8c098073ef3db2 Mon Sep 17 00:00:00 2001 From: Herbert Xu Date: Wed, 3 Feb 2016 21:39:24 +0800 Subject: crypto: algif_skcipher - Do not assume that req is unchanged The async path in algif_skcipher assumes that the crypto completion function will be called with the original request. This is not necessarily the case. In fact there is no need for this anyway since we already embed information into the request with struct skcipher_async_req. This patch adds a pointer to that struct and then passes it as the data to the callback function. Cc: stable@vger.kernel.org Signed-off-by: Herbert Xu Tested-by: Tadeusz Struk --- crypto/algif_skcipher.c | 60 +++++++++++++++++++++++-------------------------- 1 file changed, 28 insertions(+), 32 deletions(-) diff --git a/crypto/algif_skcipher.c b/crypto/algif_skcipher.c index 38c1aa89..ec07a864 100644 --- a/crypto/algif_skcipher.c +++ b/crypto/algif_skcipher.c @@ -65,18 +65,10 @@ struct skcipher_async_req { struct skcipher_async_rsgl first_sgl; struct list_head list; struct scatterlist *tsg; - char iv[]; + atomic_t *inflight; + struct skcipher_request req; }; -#define GET_SREQ(areq, ctx) (struct skcipher_async_req *)((char *)areq + \ - crypto_skcipher_reqsize(crypto_skcipher_reqtfm(&ctx->req))) - -#define GET_REQ_SIZE(ctx) \ - crypto_skcipher_reqsize(crypto_skcipher_reqtfm(&ctx->req)) - -#define GET_IV_SIZE(ctx) \ - crypto_skcipher_ivsize(crypto_skcipher_reqtfm(&ctx->req)) - #define MAX_SGL_ENTS ((4096 - sizeof(struct skcipher_sg_list)) / \ sizeof(struct scatterlist) - 1) @@ -102,15 +94,12 @@ static void skcipher_free_async_sgls(struct skcipher_async_req *sreq) static void skcipher_async_cb(struct crypto_async_request *req, int err) { - struct sock *sk = req->data; - struct alg_sock *ask = alg_sk(sk); - struct skcipher_ctx *ctx = ask->private; - struct skcipher_async_req *sreq = GET_SREQ(req, ctx); + struct skcipher_async_req *sreq = req->data; struct kiocb *iocb = sreq->iocb; - atomic_dec(&ctx->inflight); + atomic_dec(sreq->inflight); skcipher_free_async_sgls(sreq); - kfree(req); + kzfree(sreq); iocb->ki_complete(iocb, err, err); } @@ -509,37 +498,42 @@ static int skcipher_recvmsg_async(struct socket *sock, struct msghdr *msg, { struct sock *sk = sock->sk; struct alg_sock *ask = alg_sk(sk); + struct sock *psk = ask->parent; + struct alg_sock *pask = alg_sk(psk); struct skcipher_ctx *ctx = ask->private; + struct skcipher_tfm *skc = pask->private; + struct crypto_skcipher *tfm = skc->skcipher; struct skcipher_sg_list *sgl; struct scatterlist *sg; struct skcipher_async_req *sreq; struct skcipher_request *req; struct skcipher_async_rsgl *last_rsgl = NULL; unsigned int txbufs = 0, len = 0, tx_nents = skcipher_all_sg_nents(ctx); - unsigned int reqlen = sizeof(struct skcipher_async_req) + - GET_REQ_SIZE(ctx) + GET_IV_SIZE(ctx); + unsigned int reqsize = crypto_skcipher_reqsize(tfm); + unsigned int ivsize = crypto_skcipher_ivsize(tfm); int err = -ENOMEM; bool mark = false; + char *iv; - lock_sock(sk); - req = kmalloc(reqlen, GFP_KERNEL); - if (unlikely(!req)) - goto unlock; + sreq = kzalloc(sizeof(*sreq) + reqsize + ivsize, GFP_KERNEL); + if (unlikely(!sreq)) + goto out; - sreq = GET_SREQ(req, ctx); + req = &sreq->req; + iv = (char *)(req + 1) + reqsize; sreq->iocb = msg->msg_iocb; - memset(&sreq->first_sgl, '\0', sizeof(struct skcipher_async_rsgl)); INIT_LIST_HEAD(&sreq->list); + sreq->inflight = &ctx->inflight; + + lock_sock(sk); sreq->tsg = kcalloc(tx_nents, sizeof(*sg), GFP_KERNEL); - if (unlikely(!sreq->tsg)) { - kfree(req); + if (unlikely(!sreq->tsg)) goto unlock; - } sg_init_table(sreq->tsg, tx_nents); - memcpy(sreq->iv, ctx->iv, GET_IV_SIZE(ctx)); - skcipher_request_set_tfm(req, crypto_skcipher_reqtfm(&ctx->req)); + memcpy(iv, ctx->iv, ivsize); + skcipher_request_set_tfm(req, tfm); skcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG, - skcipher_async_cb, sk); + skcipher_async_cb, sreq); while (iov_iter_count(&msg->msg_iter)) { struct skcipher_async_rsgl *rsgl; @@ -615,20 +609,22 @@ static int skcipher_recvmsg_async(struct socket *sock, struct msghdr *msg, sg_mark_end(sreq->tsg + txbufs - 1); skcipher_request_set_crypt(req, sreq->tsg, sreq->first_sgl.sgl.sg, - len, sreq->iv); + len, iv); err = ctx->enc ? crypto_skcipher_encrypt(req) : crypto_skcipher_decrypt(req); if (err == -EINPROGRESS) { atomic_inc(&ctx->inflight); err = -EIOCBQUEUED; + sreq = NULL; goto unlock; } free: skcipher_free_async_sgls(sreq); - kfree(req); unlock: skcipher_wmem_wakeup(sk); release_sock(sk); + kzfree(sreq); +out: return err; } -- cgit v1.2.3 From 200c6f29cd31c466433420d5cddcad1201b2a79a Mon Sep 17 00:00:00 2001 From: Herbert Xu Date: Wed, 3 Feb 2016 21:39:26 +0800 Subject: crypto: algif_skcipher - Do not dereference ctx without socket lock Any access to non-constant bits of the private context must be done under the socket lock, in particular, this includes ctx->req. This patch moves such accesses under the lock, and fetches the tfm from the parent socket which is guaranteed to be constant, rather than from ctx->req. Cc: stable@vger.kernel.org Signed-off-by: Herbert Xu --- crypto/algif_skcipher.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/crypto/algif_skcipher.c b/crypto/algif_skcipher.c index ec07a864..ef84353e 100644 --- a/crypto/algif_skcipher.c +++ b/crypto/algif_skcipher.c @@ -295,8 +295,11 @@ static int skcipher_sendmsg(struct socket *sock, struct msghdr *msg, { struct sock *sk = sock->sk; struct alg_sock *ask = alg_sk(sk); + struct sock *psk = ask->parent; + struct alg_sock *pask = alg_sk(psk); struct skcipher_ctx *ctx = ask->private; - struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(&ctx->req); + struct skcipher_tfm *skc = pask->private; + struct crypto_skcipher *tfm = skc->skcipher; unsigned ivsize = crypto_skcipher_ivsize(tfm); struct skcipher_sg_list *sgl; struct af_alg_control con = {}; @@ -508,7 +511,7 @@ static int skcipher_recvmsg_async(struct socket *sock, struct msghdr *msg, struct skcipher_async_req *sreq; struct skcipher_request *req; struct skcipher_async_rsgl *last_rsgl = NULL; - unsigned int txbufs = 0, len = 0, tx_nents = skcipher_all_sg_nents(ctx); + unsigned int txbufs = 0, len = 0, tx_nents; unsigned int reqsize = crypto_skcipher_reqsize(tfm); unsigned int ivsize = crypto_skcipher_ivsize(tfm); int err = -ENOMEM; @@ -526,6 +529,7 @@ static int skcipher_recvmsg_async(struct socket *sock, struct msghdr *msg, sreq->inflight = &ctx->inflight; lock_sock(sk); + tx_nents = skcipher_all_sg_nents(ctx); sreq->tsg = kcalloc(tx_nents, sizeof(*sg), GFP_KERNEL); if (unlikely(!sreq->tsg)) goto unlock; @@ -633,9 +637,12 @@ static int skcipher_recvmsg_sync(struct socket *sock, struct msghdr *msg, { struct sock *sk = sock->sk; struct alg_sock *ask = alg_sk(sk); + struct sock *psk = ask->parent; + struct alg_sock *pask = alg_sk(psk); struct skcipher_ctx *ctx = ask->private; - unsigned bs = crypto_skcipher_blocksize(crypto_skcipher_reqtfm( - &ctx->req)); + struct skcipher_tfm *skc = pask->private; + struct crypto_skcipher *tfm = skc->skcipher; + unsigned bs = crypto_skcipher_blocksize(tfm); struct skcipher_sg_list *sgl; struct scatterlist *sg; int err = -EAGAIN; -- cgit v1.2.3 From 5da64d0814134dc3542fb314a66dcdf74e8553bd Mon Sep 17 00:00:00 2001 From: Herbert Xu Date: Wed, 3 Feb 2016 21:39:27 +0800 Subject: crypto: algif_skcipher - Do not set MAY_BACKLOG on the async path The async path cannot use MAY_BACKLOG because it is not meant to block, which is what MAY_BACKLOG does. On the other hand, both the sync and async paths can make use of MAY_SLEEP. Cc: stable@vger.kernel.org Signed-off-by: Herbert Xu --- crypto/algif_skcipher.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/crypto/algif_skcipher.c b/crypto/algif_skcipher.c index ef84353e..28556fce 100644 --- a/crypto/algif_skcipher.c +++ b/crypto/algif_skcipher.c @@ -536,7 +536,7 @@ static int skcipher_recvmsg_async(struct socket *sock, struct msghdr *msg, sg_init_table(sreq->tsg, tx_nents); memcpy(iv, ctx->iv, ivsize); skcipher_request_set_tfm(req, tfm); - skcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG, + skcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP, skcipher_async_cb, sreq); while (iov_iter_count(&msg->msg_iter)) { @@ -950,7 +950,8 @@ static int skcipher_accept_parent_nokey(void *private, struct sock *sk) ask->private = ctx; skcipher_request_set_tfm(&ctx->req, skcipher); - skcipher_request_set_callback(&ctx->req, CRYPTO_TFM_REQ_MAY_BACKLOG, + skcipher_request_set_callback(&ctx->req, CRYPTO_TFM_REQ_MAY_SLEEP | + CRYPTO_TFM_REQ_MAY_BACKLOG, af_alg_complete, &ctx->completion); sk->sk_destruct = skcipher_sock_destruct; -- cgit v1.2.3