/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]>
---
fs/proc/base.c | 5 +++++
1 file changed, 5 insertions(+)
--- 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.
--
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