proc: save 2 atomic ops on write to "/proc/*/attr/*"
authorAlexey Dobriyan <adobriyan@gmail.com>
Wed, 22 Aug 2018 04:54:30 +0000 (21:54 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Wed, 22 Aug 2018 17:52:45 +0000 (10:52 -0700)
commit41089b6d3e44a895076cc8ce56b08e463cb4f796
tree1ecc2775586c88c324f6fc9987c4ab2ca2f6b9a3
parenta44937fe4ef6a1190576492017939df636f4e38e
proc: save 2 atomic ops on write to "/proc/*/attr/*"

Code checks if write is done by current to its own attributes.
For that get/put pair is unnecessary as it can be done under RCU.

Note: rcu_read_unlock() can be done even earlier since pointer to a task
is not dereferenced. It depends if /proc code should look scary or not:

rcu_read_lock();
task = pid_task(...);
rcu_read_unlock();
if (!task)
return -ESRCH;
if (task != current)
return -EACCESS:

P.S.: rename "length" variable. Code like this

length = -EINVAL;

should not exist.

Link: http://lkml.kernel.org/r/20180627200218.GF18113@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
fs/proc/base.c