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

/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 <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
mrcsosa · Jul 17, 2015 · 3581d45 · 3581d45
1 parent c9d120b
commit 3581d45
Showing 1 changed file with 5 additions and 0 deletions.
diff --git a/fs/proc/base.c b/fs/proc/base.c
@@ -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.