[PATCH 6.19 601/781] pidfs: return -EREMOTE when PIDFD_GET_INFO is called on another ns

Greg Kroah-Hartman
2026-02-25T01:38:09Z

From: Luca Boccassi <luca.boccassi@gmail.com>

[ Upstream commit ab89060fbc92edd6e852bf0f533f29140afabe0e ]

Currently it is not possible to distinguish between the case where a
process has already exited and the case where a process is in a
different namespace, as both return -ESRCH.
glibc's pidfd_getpid() procfs-based implementation returns -EREMOTE
in the latter, so that distinguishing the two is possible, as the
fdinfo in procfs will list '0' as the PID in that case:

https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/pidfd_getpid.c;h=860829cf07da2267484299ccb02861822c0d07b4;hb=HEAD#l121

Change the error code so that the kernel also returns -EREMOTE in
that case.

Fixes: 7477d7dce48a ("pidfs: allow to retrieve exit information")

Signed-off-by: Luca Boccassi <luca.boccassi@gmail.com>
Link: https://patch.msgid.link/20260127225209.2293342-1-luca.boccassi@gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/pidfs.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/pidfs.c b/fs/pidfs.c
index 1e20e36e0ed55..d18c51513f6c5 100644
--- a/fs/pidfs.c
+++ b/fs/pidfs.c
@@ -329,7 +329,7 @@ static long pidfd_info(struct file *file, unsigned int cmd, unsigned long arg)
* namespace hierarchy.
*/
if (!pid_in_current_pidns(pid))
- return -ESRCH;
+ return -EREMOTE;

attr = READ_ONCE(pid->attr);
if (mask & PIDFD_INFO_EXIT) {
--
2.51.0