4.14-stable review patch. If anyone has any objections, please let me know.
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From: David Howells dhowells@redhat.com
[ Upstream commit a16b8d0cf2ec1e626d24bc2a7b9e64ace6f7501d ]
Due to a check recently added to copy_to_user(), it's now not permitted to copy from slab-held data to userspace unless the slab is whitelisted. This affects rxrpc_recvmsg() when it attempts to place an RXRPC_USER_CALL_ID control message in the userspace control message buffer. A warning is generated by usercopy_warn() because the source is the copy of the user_call_ID retained in the rxrpc_call struct.
Work around the issue by copying the user_call_ID to a variable on the stack and passing that to put_cmsg().
The warning generated looks like:
Bad or missing usercopy whitelist? Kernel memory exposure attempt detected from SLUB object 'dmaengine-unmap-128' (offset 680, size 8)! WARNING: CPU: 0 PID: 1401 at mm/usercopy.c:81 usercopy_warn+0x7e/0xa0 ... RIP: 0010:usercopy_warn+0x7e/0xa0 ... Call Trace: __check_object_size+0x9c/0x1a0 put_cmsg+0x98/0x120 rxrpc_recvmsg+0x6fc/0x1010 [rxrpc] ? finish_wait+0x80/0x80 ___sys_recvmsg+0xf8/0x240 ? __clear_rsb+0x25/0x3d ? __clear_rsb+0x15/0x3d ? __clear_rsb+0x25/0x3d ? __clear_rsb+0x15/0x3d ? __clear_rsb+0x25/0x3d ? __clear_rsb+0x15/0x3d ? __clear_rsb+0x25/0x3d ? __clear_rsb+0x15/0x3d ? finish_task_switch+0xa6/0x2b0 ? trace_hardirqs_on_caller+0xed/0x180 ? _raw_spin_unlock_irq+0x29/0x40 ? __sys_recvmsg+0x4e/0x90 __sys_recvmsg+0x4e/0x90 do_syscall_64+0x7a/0x220 entry_SYSCALL_64_after_hwframe+0x26/0x9b
Reported-by: Jonathan Billings jsbillings@jsbillings.org Signed-off-by: David Howells dhowells@redhat.com Acked-by: Kees Cook keescook@chromium.org Tested-by: Jonathan Billings jsbillings@jsbillings.org Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/rxrpc/recvmsg.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
--- a/net/rxrpc/recvmsg.c +++ b/net/rxrpc/recvmsg.c @@ -513,9 +513,10 @@ try_again: ret = put_cmsg(msg, SOL_RXRPC, RXRPC_USER_CALL_ID, sizeof(unsigned int), &id32); } else { + unsigned long idl = call->user_call_ID; + ret = put_cmsg(msg, SOL_RXRPC, RXRPC_USER_CALL_ID, - sizeof(unsigned long), - &call->user_call_ID); + sizeof(unsigned long), &idl); } if (ret < 0) goto error_unlock_call;