From 04d168c6d42d1772d35372301a14bb20784c81c5 Mon Sep 17 00:00:00 2001
From: Jakob Koschel <jakobkoschel@gmail.com>
Date: Fri, 29 Apr 2022 14:37:59 -0700
Subject: [PATCH] fs/proc/kcore.c: remove check of list iterator against head
past the loop body
When list_for_each_entry() completes the iteration over the whole list
without breaking the loop, the iterator value will be a bogus pointer
computed based on the head element.
While it is safe to use the pointer to determine if it was computed based
on the head element, either with list_entry_is_head() or &pos->member ==
head, using the iterator variable after the loop should be avoided.
In preparation to limit the scope of a list iterator to the list traversal
loop, use a dedicated pointer to point to the found element [1].
[akpm@linux-foundation.org: reduce scope of `iter']
Link: https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/ [1]
Link: https://lkml.kernel.org/r/20220331223700.902556-1-jakobkoschel@gmail.com
Signed-off-by: Jakob Koschel <jakobkoschel@gmail.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: "Brian Johannesmeyer" <bjohannesmeyer@gmail.com>
Cc: Cristiano Giuffrida <c.giuffrida@vu.nl>
Cc: "Bos, H.J." <h.j.bos@vu.nl>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
fs/proc/kcore.c | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)
diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c
index 982e694aae77..dff921f7ca33 100644
--- a/fs/proc/kcore.c
+++ b/fs/proc/kcore.c
@@ -479,10 +479,15 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
* the previous entry, search for a matching entry.
*/
if (!m || start < m->addr || start >= m->addr + m->size) {
- list_for_each_entry(m, &kclist_head, list) {
- if (start >= m->addr &&
- start < m->addr + m->size)
+ struct kcore_list *iter;
+
+ m = NULL;
+ list_for_each_entry(iter, &kclist_head, list) {
+ if (start >= iter->addr &&
+ start < iter->addr + iter->size) {
+ m = iter;
break;
+ }
}
}
@@ -492,12 +497,11 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
page_offline_freeze();
}
- if (&m->list == &kclist_head) {
+ if (!m) {
if (clear_user(buffer, tsz)) {
ret = -EFAULT;
goto out;
}
- m = NULL; /* skip the list anchor */
goto skip;
}