* + proc-alloc-path_max-bytes-for-proc-pid-fd-symlinks.patch added to -mm tree
@ 2022-01-25 0:13 akpm
0 siblings, 0 replies; only message in thread
From: akpm @ 2022-01-25 0:13 UTC (permalink / raw)
To: adobriyan, christian.brauner, haolee.swjtu, jamorris, keescook,
mm-commits
The patch titled
Subject: proc: alloc PATH_MAX bytes for /proc/${pid}/fd/ symlinks
has been added to the -mm tree. Its filename is
proc-alloc-path_max-bytes-for-proc-pid-fd-symlinks.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/proc-alloc-path_max-bytes-for-proc-pid-fd-symlinks.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/proc-alloc-path_max-bytes-for-proc-pid-fd-symlinks.patch
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------------------------------------------------------
From: Hao Lee <haolee.swjtu@gmail.com>
Subject: proc: alloc PATH_MAX bytes for /proc/${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
Link: https://lkml.kernel.org/r/Ye1fCxyZZ0I5lgOL@localhost.localdomain
Signed-off-by: Hao Lee <haolee.swjtu@gmail.com>
Signed-off-by: Alexey 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: Andrew Morton <akpm@linux-foundation.org>
---
fs/proc/base.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
--- a/fs/proc/base.c~proc-alloc-path_max-bytes-for-proc-pid-fd-symlinks
+++ a/fs/proc/base.c
@@ -1764,25 +1764,25 @@ out:
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;
}
_
Patches currently in -mm which might be from haolee.swjtu@gmail.com are
proc-alloc-path_max-bytes-for-proc-pid-fd-symlinks.patch
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2022-01-25 0:13 + proc-alloc-path_max-bytes-for-proc-pid-fd-symlinks.patch added to -mm tree akpm
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