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/proc/$PID/cmdline: fixup empty ARGV case

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/proc/*/cmdline code checks if it should look at ENVP area by checking
last byte of ARGV area:

	rv = access_remote_vm(mm, arg_end - 1, &c, 1, 0);
	if (rv <= 0)
		goto out_free_page;

If ARGV is somehow made empty (by doing execve(..., NULL, ...) or
manually setting ->arg_start and ->arg_end to equal values), the decision
will be based on byte which doesn't even belong to ARGV/ENVP.

So, quickly check if ARGV area is empty and report 0 to match previous
behaviour.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Alexey Dobriyan 2015-07-17 16:24:09 -07:00 committed by Linus Torvalds
parent c9d120b0b2
commit 3581d458c3
1 changed files with 5 additions and 0 deletions
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5
fs/proc/base.c
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@ -243,6 +243,11 @@ static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf,
len1 = arg_end - arg_start;
len2 = env_end - env_start;
/* Empty ARGV. */
if (len1 == 0) {
rv = 0;
goto out_free_page;
}
/*
* Inherently racy -- command line shares address space
* with code and data.