Messages in this thread |  | | From | Stanisław Busza <> | Date | Wed, 1 Feb 2017 14:37:33 +0100 | Subject | [BUG] Probably bug concerning write to /proc/self/loginuid |
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Hello, this is my first message to the linux kernel development list.
I probably found a bug in the linux kernel.
It affects all kernels since 2.6.12, especially 4.9 that i use.
Lets take a look at the file: fs/proc/base.c and function proc_loginuid_write() (circa 1264 line):
static ssize_t proc_loginuid_write(struct file * file, const char __user * buf, size_t count, loff_t *ppos) { struct inode * inode = file_inode(file); uid_t loginuid; kuid_t kloginuid; int rv;
/* here is check that is interesting for us */ rcu_read_lock(); if (current != pid_task(proc_pid(inode), PIDTYPE_PID)) { rcu_read_unlock(); return -EPERM; } rcu_read_unlock();
I marked with comment the place where function checks which process is writing to file.
Problem occurs when multithreaded application tries to write /proc/self/loginuid.
For first thread that is spawned write succeeds. For any other thread write fails (threads have different pids in linux).
So my question is whether this is a bug or intentional behavior.
---------------------------------------------------------- Stanisław Busza
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