a447da7d00
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>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.