Patch series "taskstats: fix cgroupstats invalid fd handling and add
selftests".
This series fixes an issue where cgroupstats mishandles invalid file
descriptors, and introduces a functional kselftest to prevent regressions.
When an invalid file descriptor is passed via CGROUPSTATS_CMD_ATTR_FD,
cgroupstats_user_cmd() returns 0 instead of an error code. This leads to
two broken behaviors depending on netlink flags:
- Callers without NLM_F_ACK block indefinitely on recv().
- Callers with NLM_F_ACK receive a misleading success ACK (errno == 0)
but no actual statistics payload.
The first patch addresses this by returning -EBADF when the fd cannot be
resolved. The second patch adds a comprehensive kselftest covering both
the valid cgroup v1 query and the invalid fd paths (with and without
NLM_F_ACK) to ensure the fixes work as intended.
This patch (of 2):
cgroupstats_user_cmd() returns 0 without sending a reply or a netlink
error when the fd passed via CGROUPSTATS_CMD_ATTR_FD does not resolve to
an open file in the caller's table. As a result:
- clients that did not set NLM_F_ACK block on recv() indefinitely
waiting for a CGROUPSTATS_CMD_NEW message that is never emitted;
- clients that set NLM_F_ACK receive a misleading "success" ACK (errno
== 0) with no statistics payload.
Return -EBADF instead so the netlink layer propagates the error to
userspace as expected.
Link: https://lore.kernel.org/cover.1783713230.git.cyyzero16@gmail.com
Link: https://lore.kernel.org/b4fd9e288e4a48efebaf41b4ffcdb204b06675c4.1783713230.git.cyyzero16@gmail.com
Signed-off-by: Yiyang Chen <cyyzero16@gmail.com>
Acked-by: Balbir Singh <balbirs@nvidia.com>
Cc: Dr. Thomas Orgis <thomas.orgis@uni-hamburg.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
b0860c1df2