Commit 3a72917c authored by Hao Lee's avatar Hao Lee Committed by Linus Torvalds
Browse files

proc: alloc PATH_MAX bytes for /proc/${pid}/fd/ symlinks 

It's not a standard approach that use __get_free_page() to alloc path
buffer directly.  We'd better use kmalloc and PATH_MAX.

	PAGE_SIZE is different on different archs. An unlinked file
	with very long canonical pathname will readlink differently
	because "(deleted)" eats into a buffer.	--adobriyan

[akpm@linux-foundation.org: remove now-unneeded cast]

Link: https://lkml.kernel.org/r/Ye1fCxyZZ0I5lgOL@localhost.localdomain


Signed-off-by: default avatarHao Lee <haolee.swjtu@gmail.com>
Signed-off-by: default avatarAlexey Dobriyan <adobriyan@gmail.com>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: James Morris <jamorris@linux.microsoft.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent f443e374

fs/proc/base.c

+4 −4
Original line number Diff line number Diff line
@@ -1764,25 +1764,25 @@ static const char *proc_pid_get_link(struct dentry *dentry, 


static int do_proc_readlink(struct path *path, char __user *buffer, int buflen)

{

	char *tmp = (char *)__get_free_page(GFP_KERNEL);

	char *tmp = kmalloc(PATH_MAX, GFP_KERNEL);

	char *pathname;

	int len;



	if (!tmp)

		return -ENOMEM;



	pathname = d_path(path, tmp, PAGE_SIZE);

	pathname = d_path(path, tmp, PATH_MAX);

	len = PTR_ERR(pathname);

	if (IS_ERR(pathname))

		goto out;

	len = tmp + PAGE_SIZE - 1 - pathname;

	len = tmp + PATH_MAX - 1 - pathname;



	if (len > buflen)

		len = buflen;

	if (copy_to_user(buffer, pathname, len))

		len = -EFAULT;

 out:

	free_page((unsigned long)tmp);

	kfree(tmp);

	return len;

}