From: Eric Dumazet edumazet@google.com
commit d42ee76ecb6c49d499fc5eb32ca34468d95dbc3e upstream.
After freeing ep->auth_hmacs we have to clear the pointer or risk use-after-free as reported by syzbot:
BUG: KASAN: use-after-free in sctp_auth_destroy_hmacs net/sctp/auth.c:509 [inline] BUG: KASAN: use-after-free in sctp_auth_destroy_hmacs net/sctp/auth.c:501 [inline] BUG: KASAN: use-after-free in sctp_auth_free+0x17e/0x1d0 net/sctp/auth.c:1070 Read of size 8 at addr ffff8880a8ff52c0 by task syz-executor941/6874
CPU: 0 PID: 6874 Comm: syz-executor941 Not tainted 5.9.0-rc8-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x198/0x1fd lib/dump_stack.c:118 print_address_description.constprop.0.cold+0xae/0x497 mm/kasan/report.c:383 __kasan_report mm/kasan/report.c:513 [inline] kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530 sctp_auth_destroy_hmacs net/sctp/auth.c:509 [inline] sctp_auth_destroy_hmacs net/sctp/auth.c:501 [inline] sctp_auth_free+0x17e/0x1d0 net/sctp/auth.c:1070 sctp_endpoint_destroy+0x95/0x240 net/sctp/endpointola.c:203 sctp_endpoint_put net/sctp/endpointola.c:236 [inline] sctp_endpoint_free+0xd6/0x110 net/sctp/endpointola.c:183 sctp_destroy_sock+0x9c/0x3c0 net/sctp/socket.c:4981 sctp_v6_destroy_sock+0x11/0x20 net/sctp/socket.c:9415 sk_common_release+0x64/0x390 net/core/sock.c:3254 sctp_close+0x4ce/0x8b0 net/sctp/socket.c:1533 inet_release+0x12e/0x280 net/ipv4/af_inet.c:431 inet6_release+0x4c/0x70 net/ipv6/af_inet6.c:475 __sock_release+0xcd/0x280 net/socket.c:596 sock_close+0x18/0x20 net/socket.c:1277 __fput+0x285/0x920 fs/file_table.c:281 task_work_run+0xdd/0x190 kernel/task_work.c:141 exit_task_work include/linux/task_work.h:25 [inline] do_exit+0xb7d/0x29f0 kernel/exit.c:806 do_group_exit+0x125/0x310 kernel/exit.c:903 __do_sys_exit_group kernel/exit.c:914 [inline] __se_sys_exit_group kernel/exit.c:912 [inline] __x64_sys_exit_group+0x3a/0x50 kernel/exit.c:912 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x43f278 Code: Bad RIP value. RSP: 002b:00007fffe0995c38 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000043f278 RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000000 RBP: 00000000004bf068 R08: 00000000000000e7 R09: ffffffffffffffd0 R10: 0000000020000000 R11: 0000000000000246 R12: 0000000000000001 R13: 00000000006d1180 R14: 0000000000000000 R15: 0000000000000000
Allocated by task 6874: kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48 kasan_set_track mm/kasan/common.c:56 [inline] __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:461 kmem_cache_alloc_trace+0x174/0x300 mm/slab.c:3554 kmalloc include/linux/slab.h:554 [inline] kmalloc_array include/linux/slab.h:593 [inline] kcalloc include/linux/slab.h:605 [inline] sctp_auth_init_hmacs+0xdb/0x3b0 net/sctp/auth.c:464 sctp_auth_init+0x8a/0x4a0 net/sctp/auth.c:1049 sctp_setsockopt_auth_supported net/sctp/socket.c:4354 [inline] sctp_setsockopt+0x477e/0x97f0 net/sctp/socket.c:4631 __sys_setsockopt+0x2db/0x610 net/socket.c:2132 __do_sys_setsockopt net/socket.c:2143 [inline] __se_sys_setsockopt net/socket.c:2140 [inline] __x64_sys_setsockopt+0xba/0x150 net/socket.c:2140 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xa9
Freed by task 6874: kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48 kasan_set_track+0x1c/0x30 mm/kasan/common.c:56 kasan_set_free_info+0x1b/0x30 mm/kasan/generic.c:355 __kasan_slab_free+0xd8/0x120 mm/kasan/common.c:422 __cache_free mm/slab.c:3422 [inline] kfree+0x10e/0x2b0 mm/slab.c:3760 sctp_auth_destroy_hmacs net/sctp/auth.c:511 [inline] sctp_auth_destroy_hmacs net/sctp/auth.c:501 [inline] sctp_auth_init_hmacs net/sctp/auth.c:496 [inline] sctp_auth_init_hmacs+0x2b7/0x3b0 net/sctp/auth.c:454 sctp_auth_init+0x8a/0x4a0 net/sctp/auth.c:1049 sctp_setsockopt_auth_supported net/sctp/socket.c:4354 [inline] sctp_setsockopt+0x477e/0x97f0 net/sctp/socket.c:4631 __sys_setsockopt+0x2db/0x610 net/socket.c:2132 __do_sys_setsockopt net/socket.c:2143 [inline] __se_sys_setsockopt net/socket.c:2140 [inline] __x64_sys_setsockopt+0xba/0x150 net/socket.c:2140 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xa9
Fixes: 1f485649f529 ("[SCTP]: Implement SCTP-AUTH internals") Signed-off-by: Eric Dumazet edumazet@google.com Cc: Vlad Yasevich vyasevich@gmail.com Cc: Neil Horman nhorman@tuxdriver.com Cc: Marcelo Ricardo Leitner marcelo.leitner@gmail.com Acked-by: Marcelo Ricardo Leitner marcelo.leitner@gmail.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- net/sctp/auth.c | 1 + 1 file changed, 1 insertion(+)
--- a/net/sctp/auth.c +++ b/net/sctp/auth.c @@ -493,6 +493,7 @@ int sctp_auth_init_hmacs(struct sctp_end out_err: /* Clean up any successful allocations */ sctp_auth_destroy_hmacs(ep->auth_hmacs); + ep->auth_hmacs = NULL; return -ENOMEM; }