Commit 04d168c6 authored Apr 29, 2022 by Jakob Koschel Committed by Andrew Morton Apr 29, 2022

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>

parent f1e75d12

fs/proc/kcore.c

+9 −5

Original line number	Diff line number	Diff line
		@@ -479,12 +479,17 @@ 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;
		}
		}
		}

		if (page_offline_frozen++ % MAX_ORDER_NR_PAGES == 0) {
		page_offline_thaw();
		@@ -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;
		}