From: Jakob Koschel Subject: 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]. 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 Cc: Mike Rapoport Cc: David Hildenbrand Cc: Oscar Salvador Cc: "Brian Johannesmeyer" Cc: Cristiano Giuffrida Cc: "Bos, H.J." Cc: Alexey Dobriyan Signed-off-by: Andrew Morton --- fs/proc/kcore.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) --- a/fs/proc/kcore.c~fs-proc-kcorec-remove-check-of-list-iterator-against-head-past-the-loop-body +++ a/fs/proc/kcore.c @@ -316,6 +316,7 @@ read_kcore(struct file *file, char __use size_t page_offline_frozen = 1; size_t phdrs_len, notes_len; struct kcore_list *m; + struct kcore_list *iter; size_t tsz; int nphdr; unsigned long start; @@ -479,10 +480,13 @@ read_kcore(struct file *file, char __use * 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) + m = NULL; + list_for_each_entry(iter, &kclist_head, list) { + if (start >= iter->addr && + start < iter->addr + iter->size) { + m = iter; break; + } } } @@ -492,12 +496,11 @@ read_kcore(struct file *file, char __use 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; } _