Greg Kurz a85222435b net/9p: avoid -ERESTARTSYS leak to userspace ... If it was interrupted by a signal, the 9p client may need to send some more requests to the server for cleanup before returning to userspace. To avoid such a last minute request to be interrupted right away, the client memorizes if a signal is pending, clears TIF_SIGPENDING, handles the request and calls recalc_sigpending() before returning. Unfortunately, if the transmission of this cleanup request fails for any reason, the transport returns an error and the client propagates it right away, without calling recalc_sigpending(). This ends up with -ERESTARTSYS from the initially interrupted request crawling up to syscall exit, with TIF_SIGPENDING cleared by the cleanup request. The specific signal handling code, which is responsible for converting -ERESTARTSYS to -EINTR is not called, and userspace receives the confusing errno value: open: Unknown error 512 (512) This is really hard to hit in real life. I discovered the issue while working on hot-unplug of a virtio-9p-pci device with an instrumented QEMU allowing to control request completion. Both p9_client_zc_rpc() and p9_client_rpc() functions have this buggy error path actually. Their code flow is a bit obscure and the best thing to do would probably be a full rewrite: to really ensure this situation of clearing TIF_SIGPENDING and returning -ERESTARTSYS can never happen. But given the general lack of interest for the 9p code, I won't risk breaking more things. So this patch simply fixes the buggy paths in both functions with a trivial label+goto. Thanks to Laurent Dufour for his help and suggestions on how to find the root cause and how to fix it. Link: http://lkml.kernel.org/r/152062809886.10599.7361006774123053312.stgit@bahia.lan Signed-off-by: Greg Kurz <groug@kaod.org> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Yiwen Jiang <jiangyiwen@huawei.com> Cc: Eric Van Hensbergen <ericvh@gmail.com> Cc: Ron Minnich <rminnich@sandia.gov> Cc: Latchesar Ionkov <lucho@ionkov.net> Cc: David Miller <davem@davemloft.net> Cc: Laurent Dufour <ldufour@linux.vnet.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2018-04-05 21:36:22 -07:00
..
client.c	net/9p: avoid -ERESTARTSYS leak to userspace	2018-04-05 21:36:22 -07:00
error.c
Kconfig
Makefile	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
mod.c
protocol.c
protocol.h
trans_common.c
trans_common.h
trans_fd.c	vfs: do bulk POLL* -> EPOLL* replacement	2018-02-11 14:34:03 -08:00
trans_rdma.c	9p: Implement show_options	2017-07-11 06:08:58 -04:00
trans_virtio.c	9p/trans_virtio: discard zero-length reply	2018-02-09 20:08:19 +02:00
trans_xen.c	9p: add missing module license for xen transport	2018-01-15 13:13:53 -05:00
util.c