Messages in this thread Patch in this message | | | Date | Sun, 23 Jan 2022 16:58:35 +0300 | From | Alexey Dobriyan <> | Subject | [PATCH v2] proc: alloc PATH_MAX bytes for /proc/${pid}/fd/ symlinks |
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From: Hao Lee <haolee.swjtu@gmail.com>
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
Signed-off-by: Hao Lee <haolee.swjtu@gmail.com> Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> ---
fs/proc/base.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
--- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -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 = (char *)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; }
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