selinux_sctp_bind_connect() must verify if the address buffer has sufficient length before accessing the 'sa_family' field. See __sctp_connect() for a similar check.
The length of the whole address ('len') is already checked in the callees.
Reported-by: Qian Cai cai@gmx.us Fixes: d452930fd3b9 ("selinux: Add SCTP support") Cc: stable@vger.kernel.org # 4.17+ Cc: Richard Haines richard_c_haines@btinternet.com Signed-off-by: Ondrej Mosnacek omosnace@redhat.com --- Hi,
On Mon, Nov 12, 2018 at 8:39 PM Qian Cai cai@gmx.us wrote:
Running the trinity fuzzer on the latest mainline (rc2) generates this,
[15029.879626] BUG: KASAN: slab-out-of-bounds in selinux_sctp_bind_connect+0x60/0x150 [15029.887275] Read of size 2 at addr ffff801ec53c5080 by task trinity-main/18081 [15029.887294] [15029.887304] CPU: 28 PID: 18081 Comm: trinity-main Tainted: G W OE 4.20.0-rc2+ #15 [15029.887311] Hardware name: Huawei TaiShan 2280 /BC11SPCD, BIOS 1.50 06/01/2018 [15000.084786] [15029.887320] Call trace: [15029.915511] dump_backtrace+0x0/0x2c8 [15029.920046] show_stack+0x24/0x30 [15029.923367] dump_stack+0x118/0x19c [15029.927539] print_address_description+0x68/0x2a0 [15029.932245] kasan_report+0x1b4/0x348 [15029.938760] __asan_load2+0x7c/0xa0 [15029.945098] selinux_sctp_bind_connect+0x60/0x150
[15029.950571] security_sctp_bind_connect+0x58/0x90 [15029.955493] __sctp_setsockopt_connectx+0x68/0x128 [sctp] [15029.960943] sctp_setsockopt+0x764/0x2928 [sctp] [15029.965564] sock_common_setsockopt+0x6c/0x80 [15029.969923] __arm64_sys_setsockopt+0x13c/0x1f0 [15029.974456] el0_svc_handler+0xd4/0x198 [15029.978293] el0_svc+0x8/0xc [15029.981174] [15029.982667] Allocated by task 18081: [15029.986245] kasan_kmalloc.part.1+0x40/0x108 [15029.990517] kasan_kmalloc+0xb4/0xc8 [15029.994094] __kmalloc_node+0x1c4/0x638 [15029.997933] kvmalloc_node+0x98/0xa8 [15030.001511] vmemdup_user+0x34/0x128 [15030.005137] __sctp_setsockopt_connectx+0x44/0x128 [sctp] [15030.010586] sctp_setsockopt+0x764/0x2928 [sctp] [15030.015205] sock_common_setsockopt+0x6c/0x80 [15030.019564] __arm64_sys_setsockopt+0x13c/0x1f0 [15030.024096] el0_svc_handler+0xd4/0x198 [15030.027933] el0_svc+0x8/0xc [15030.030814] [15030.032306] Freed by task 3025: [15030.035451] __kasan_slab_free+0x114/0x228 [15030.039548] kasan_slab_free+0x10/0x18 [15030.043299] kfree+0x114/0x408 [15030.046357] selinux_sk_free_security+0x38/0x48 [15030.050888] security_sk_free+0x3c/0x58 [15030.054727] __sk_destruct+0x3e8/0x570 [15030.058478] sk_destruct+0x4c/0x58 [15030.061881] __sk_free+0x68/0x138 [15030.065197] sk_free+0x3c/0x48 [15030.068255] unix_release_sock+0x4a8/0x550 [15030.072353] unix_release+0x34/0x50 [15030.075843] __sock_release+0x74/0x110 [15030.079593] sock_close+0x24/0x38 [15030.082913] __fput+0x1b8/0x368 [15030.086055] ____fput+0x20/0x30 [15030.089199] task_work_run+0x14c/0x1a8 [15030.092951] do_notify_resume+0x1e4/0x200 [15030.096961] work_pending+0x8/0x14 [15030.100363] [15030.101856] The buggy address belongs to the object at ffff801ec53c5080 [15030.101856] which belongs to the cache kmalloc-128 of size 128 [15030.114376] The buggy address is located 0 bytes inside of [15030.114376] 128-byte region [ffff801ec53c5080, ffff801ec53c5100) [15030.125939] The buggy address belongs to the page: [15030.130732] page:ffff7fe007b14f00 count:1 mapcount:0 mapping:ffff8016c0010480 index:0x0 [15030.138738] flags: 0x5fffff0000000200(slab) [15030.142926] raw: 5fffff0000000200 ffff7fe007980608 ffff801ec000fd60 ffff8016c0010480 [15030.150671] raw: 0000000000000000 0000000000660066 00000001ffffffff 0000000000000000 [15030.158413] page dumped because: kasan: bad access detected [15030.163984] [15030.165476] Memory state around the buggy address: [15030.170269] ffff801ec53c4f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [15030.177491] ffff801ec53c5000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [15030.184714] >ffff801ec53c5080: 01 fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [15030.191934] ^ [15030.195164] ffff801ec53c5100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [15030.202386] ffff801ec53c5180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [15030.209607] ================================================================== [15030.216828] Disabling lock debugging due to kernel taint
I think I found the cause - Qian, can you test this patch if it fixes the problem?
security/selinux/hooks.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 7ce683259357..a67459eb62d5 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -5318,6 +5318,9 @@ static int selinux_sctp_bind_connect(struct sock *sk, int optname, addr_buf = address;
while (walk_size < addrlen) { + if (walk_size + sizeof(sa_family_t) > addrlen) + return -EINVAL; + addr = addr_buf; switch (addr->sa_family) { case AF_UNSPEC: