4.17-stable review patch. If anyone has any objections, please let me know.
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From: Daniel Borkmann daniel@iogearbox.net
[ Upstream commit a447da7d00410278c90d3576782a43f8b675d7be ]
syzkaller managed to trigger a use-after-free in tls like the following:
BUG: KASAN: use-after-free in tls_push_record.constprop.15+0x6a2/0x810 [tls] Write of size 1 at addr ffff88037aa08000 by task a.out/2317
CPU: 3 PID: 2317 Comm: a.out Not tainted 4.17.0+ #144 Hardware name: LENOVO 20FBCTO1WW/20FBCTO1WW, BIOS N1FET47W (1.21 ) 11/28/2016 Call Trace: dump_stack+0x71/0xab print_address_description+0x6a/0x280 kasan_report+0x258/0x380 ? tls_push_record.constprop.15+0x6a2/0x810 [tls] tls_push_record.constprop.15+0x6a2/0x810 [tls] tls_sw_push_pending_record+0x2e/0x40 [tls] tls_sk_proto_close+0x3fe/0x710 [tls] ? tcp_check_oom+0x4c0/0x4c0 ? tls_write_space+0x260/0x260 [tls] ? kmem_cache_free+0x88/0x1f0 inet_release+0xd6/0x1b0 __sock_release+0xc0/0x240 sock_close+0x11/0x20 __fput+0x22d/0x660 task_work_run+0x114/0x1a0 do_exit+0x71a/0x2780 ? mm_update_next_owner+0x650/0x650 ? handle_mm_fault+0x2f5/0x5f0 ? __do_page_fault+0x44f/0xa50 ? mm_fault_error+0x2d0/0x2d0 do_group_exit+0xde/0x300 __x64_sys_exit_group+0x3a/0x50 do_syscall_64+0x9a/0x300 ? page_fault+0x8/0x30 entry_SYSCALL_64_after_hwframe+0x44/0xa9
This happened through fault injection where aead_req allocation in tls_do_encryption() eventually failed and we returned -ENOMEM from the function. Turns out that the use-after-free is triggered from tls_sw_sendmsg() in the second tls_push_record(). The error then triggers a jump to waiting for memory in sk_stream_wait_memory() resp. returning immediately in case of MSG_DONTWAIT. What follows is the trim_both_sgl(sk, orig_size), which drops elements from the sg list added via tls_sw_sendmsg(). Now the use-after-free gets triggered when the socket is being closed, where tls_sk_proto_close() callback is invoked. The tls_complete_pending_work() will figure that there's a pending closed tls record to be flushed and thus calls into the tls_push_pending_closed_record() from there. ctx->push_pending_record() is called from the latter, which is the tls_sw_push_pending_record() from sw path. This again calls into tls_push_record(). And here the tls_fill_prepend() will panic since the buffer address has been freed earlier via trim_both_sgl(). One way to fix it is to move the aead request allocation out of tls_do_encryption() early into tls_push_record(). This means we don't prep the tls header and advance state to the TLS_PENDING_CLOSED_RECORD before allocation which could potentially fail happened. That fixes the issue on my side.
Fixes: 3c4d7559159b ("tls: kernel TLS support") Reported-by: syzbot+5c74af81c547738e1684@syzkaller.appspotmail.com Reported-by: syzbot+709f2810a6a05f11d4d3@syzkaller.appspotmail.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Acked-by: Dave Watson davejwatson@fb.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/tls/tls_sw.c | 26 +++++++++++++------------- 1 file changed, 13 insertions(+), 13 deletions(-)
--- a/net/tls/tls_sw.c +++ b/net/tls/tls_sw.c @@ -191,18 +191,12 @@ static void tls_free_both_sg(struct sock }
static int tls_do_encryption(struct tls_context *tls_ctx, - struct tls_sw_context *ctx, size_t data_len, - gfp_t flags) + struct tls_sw_context *ctx, + struct aead_request *aead_req, + size_t data_len) { - unsigned int req_size = sizeof(struct aead_request) + - crypto_aead_reqsize(ctx->aead_send); - struct aead_request *aead_req; int rc;
- aead_req = kzalloc(req_size, flags); - if (!aead_req) - return -ENOMEM; - ctx->sg_encrypted_data[0].offset += tls_ctx->tx.prepend_size; ctx->sg_encrypted_data[0].length -= tls_ctx->tx.prepend_size;
@@ -219,7 +213,6 @@ static int tls_do_encryption(struct tls_ ctx->sg_encrypted_data[0].offset -= tls_ctx->tx.prepend_size; ctx->sg_encrypted_data[0].length += tls_ctx->tx.prepend_size;
- kfree(aead_req); return rc; }
@@ -228,8 +221,14 @@ static int tls_push_record(struct sock * { struct tls_context *tls_ctx = tls_get_ctx(sk); struct tls_sw_context *ctx = tls_sw_ctx(tls_ctx); + struct aead_request *req; int rc;
+ req = kzalloc(sizeof(struct aead_request) + + crypto_aead_reqsize(ctx->aead_send), sk->sk_allocation); + if (!req) + return -ENOMEM; + sg_mark_end(ctx->sg_plaintext_data + ctx->sg_plaintext_num_elem - 1); sg_mark_end(ctx->sg_encrypted_data + ctx->sg_encrypted_num_elem - 1);
@@ -245,15 +244,14 @@ static int tls_push_record(struct sock * tls_ctx->pending_open_record_frags = 0; set_bit(TLS_PENDING_CLOSED_RECORD, &tls_ctx->flags);
- rc = tls_do_encryption(tls_ctx, ctx, ctx->sg_plaintext_size, - sk->sk_allocation); + rc = tls_do_encryption(tls_ctx, ctx, req, ctx->sg_plaintext_size); if (rc < 0) { /* If we are called from write_space and * we fail, we need to set this SOCK_NOSPACE * to trigger another write_space in the future. */ set_bit(SOCK_NOSPACE, &sk->sk_socket->flags); - return rc; + goto out_req; }
free_sg(sk, ctx->sg_plaintext_data, &ctx->sg_plaintext_num_elem, @@ -268,6 +266,8 @@ static int tls_push_record(struct sock * tls_err_abort(sk, EBADMSG);
tls_advance_record_sn(sk, &tls_ctx->tx); +out_req: + kfree(req); return rc; }