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Yiyang Chen
b0860c1df2
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>