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authorRichard W.M. Jones <rjones@redhat.com>2016-05-21 03:00:05 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2016-05-21 03:58:30 +0300
commit3e42979e65dace1f9268dd5440e5ab096b8dee59 (patch)
tree152057727f5ac2448a4575cbda5937527a1ab5ba /Documentation/filesystems
parent623e47fc64f8de480b322b7ed68855f97137e2a5 (diff)
downloadlinux-3e42979e65dace1f9268dd5440e5ab096b8dee59.tar.xz
procfs: expose umask in /proc/<PID>/status
It's not possible to read the process umask without also modifying it, which is what umask(2) does. A library cannot read umask safely, especially if the main program might be multithreaded. Add a new status line ("Umask") in /proc/<PID>/status. It contains the file mode creation mask (umask) in octal. It is only shown for tasks which have task->fs. This patch is adapted from one originally written by Pierre Carrier. The use case is that we have endless trouble with people setting weird umask() values (usually on the grounds of "security"), and then everything breaking. I'm on the hook to fix these. We'd like to add debugging to our program so we can dump out the umask in debug reports. Previous versions of the patch used a syscall so you could only read your own umask. That's all I need. However there was quite a lot of push-back from those, so this new version exports it in /proc. See: https://lkml.org/lkml/2016/4/13/704 [umask2] https://lkml.org/lkml/2016/4/13/487 [getumask] Signed-off-by: Richard W.M. Jones <rjones@redhat.com> Acked-by: Konstantin Khlebnikov <koct9i@gmail.com> Acked-by: Jerome Marchand <jmarchan@redhat.com> Acked-by: Kees Cook <keescook@chromium.org> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Michal Hocko <mhocko@kernel.org> Cc: Pierre Carrier <pierre@spotify.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/filesystems')
-rw-r--r--Documentation/filesystems/proc.txt1
1 files changed, 1 insertions, 0 deletions
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index 7f5607a089b4..e8d00759bfa5 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -225,6 +225,7 @@ Table 1-2: Contents of the status files (as of 4.1)
TracerPid PID of process tracing this process (0 if not)
Uid Real, effective, saved set, and file system UIDs
Gid Real, effective, saved set, and file system GIDs
+ Umask file mode creation mask
FDSize number of file descriptor slots currently allocated
Groups supplementary group list
NStgid descendant namespace thread group ID hierarchy