[merged mm-nonmm-stable] taskstats-return-ebadf-when-cgroupstats-receives-an-invalid-fd.patch removed from -mm tree

The quilt patch titled
     Subject: taskstats: return -EBADF when cgroupstats receives an invalid fd
has been removed from the -mm tree.  Its filename was
     taskstats-return-ebadf-when-cgroupstats-receives-an-invalid-fd.patch

This patch was dropped because it was merged into the mm-nonmm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Yiyang Chen <[email protected]>
Subject: taskstats: return -EBADF when cgroupstats receives an invalid fd
Date: Sat, 11 Jul 2026 04:07:36 +0800

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/[email protected]
Link: https://lore.kernel.org/b4fd9e288e4a48efebaf41b4ffcdb204b06675c4.1783713230.git.cyyzero16@gmail.com
Signed-off-by: Yiyang Chen <[email protected]>
Acked-by: Balbir Singh <[email protected]>
Cc: Dr. Thomas Orgis <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---

 kernel/taskstats.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/taskstats.c~taskstats-return-ebadf-when-cgroupstats-receives-an-invalid-fd
+++ a/kernel/taskstats.c
@@ -423,7 +423,7 @@ static int cgroupstats_user_cmd(struct s
 	fd = nla_get_u32(info->attrs[CGROUPSTATS_CMD_ATTR_FD]);
 	CLASS(fd, f)(fd);
 	if (fd_empty(f))
-		return 0;
+		return -EBADF;
 
 	size = nla_total_size(sizeof(struct cgroupstats));
 
_

Patches currently in -mm which might be from [email protected] are