From 3581d458c39bc5e58ceeeaf51796625bc978d2eb Mon Sep 17 00:00:00 2001 From: Alexey Dobriyan Date: Fri, 17 Jul 2015 16:24:09 -0700 Subject: [PATCH] /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 Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/proc/base.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/fs/proc/base.c b/fs/proc/base.c index 87782e874b6a..aa50d1ac28fc 100644 --- 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. -- 2.30.2