diff options
| author | Kees Cook <keescook@chromium.org> | 2018-02-07 17:44:38 -0800 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2018-02-08 15:15:48 -0500 |
| commit | 79a8a642bf05cd0dced20621f6fef9d884124abd (patch) | |
| tree | 71e480e6404ec409f6f9fa6dfac7372a1c14d559 /net | |
| parent | e728789c52afccc1275cba1dd812f03abe16ea3c (diff) | |
net: Whitelist the skbuff_head_cache "cb" field
Most callers of put_cmsg() use a "sizeof(foo)" for the length argument.
Within put_cmsg(), a copy_to_user() call is made with a dynamic size, as a
result of the cmsg header calculations. This means that hardened usercopy
will examine the copy, even though it was technically a fixed size and
should be implicitly whitelisted. All the put_cmsg() calls being built
from values in skbuff_head_cache are coming out of the protocol-defined
"cb" field, so whitelist this field entirely instead of creating per-use
bounce buffers, for which there are concerns about performance.
Original report was:
Bad or missing usercopy whitelist? Kernel memory exposure attempt detected from SLAB object 'skbuff_head_cache' (offset 64, size 16)!
WARNING: CPU: 0 PID: 3663 at mm/usercopy.c:81 usercopy_warn+0xdb/0x100 mm/usercopy.c:76
...
__check_heap_object+0x89/0xc0 mm/slab.c:4426
check_heap_object mm/usercopy.c:236 [inline]
__check_object_size+0x272/0x530 mm/usercopy.c:259
check_object_size include/linux/thread_info.h:112 [inline]
check_copy_size include/linux/thread_info.h:143 [inline]
copy_to_user include/linux/uaccess.h:154 [inline]
put_cmsg+0x233/0x3f0 net/core/scm.c:242
sock_recv_errqueue+0x200/0x3e0 net/core/sock.c:2913
packet_recvmsg+0xb2e/0x17a0 net/packet/af_packet.c:3296
sock_recvmsg_nosec net/socket.c:803 [inline]
sock_recvmsg+0xc9/0x110 net/socket.c:810
___sys_recvmsg+0x2a4/0x640 net/socket.c:2179
__sys_recvmmsg+0x2a9/0xaf0 net/socket.c:2287
SYSC_recvmmsg net/socket.c:2368 [inline]
SyS_recvmmsg+0xc4/0x160 net/socket.c:2352
entry_SYSCALL_64_fastpath+0x29/0xa0
Reported-by: syzbot+e2d6cfb305e9f3911dea@syzkaller.appspotmail.com
Fixes: 6d07d1cd300f ("usercopy: Restrict non-usercopy caches to size 0")
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
| -rw-r--r-- | net/core/skbuff.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 8c61c27c1b28..09bd89c90a71 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -3894,10 +3894,12 @@ EXPORT_SYMBOL_GPL(skb_gro_receive); void __init skb_init(void) { - skbuff_head_cache = kmem_cache_create("skbuff_head_cache", + skbuff_head_cache = kmem_cache_create_usercopy("skbuff_head_cache", sizeof(struct sk_buff), 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, + offsetof(struct sk_buff, cb), + sizeof_field(struct sk_buff, cb), NULL); skbuff_fclone_cache = kmem_cache_create("skbuff_fclone_cache", sizeof(struct sk_buff_fclones), |