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Subject[PATCH 4.19 25/49] sctp: fix sctp_auth_init_hmacs() error path
Date
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
@@ -515,6 +515,7 @@ 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;
}


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