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Add check of order < 0 before calling free_pages()

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The function addresses that are traced by ftrace are stored in pages,
 and the size is held in a variable. If there's some error in creating
 them, the allocate ones will be freed. In this case, it is possible that
 the order of pages to be freed may end up being negative due to a size of
 zero passed to get_count_order(), and then that negative number will cause
 free_pages() to free a very large section. Make sure that does not happen.
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Merge tag 'trace-v5.12-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull ftrace fix from Steven Rostedt:
 "Add check of order < 0 before calling free_pages()

  The function addresses that are traced by ftrace are stored in pages,
  and the size is held in a variable. If there's some error in creating
  them, the allocate ones will be freed. In this case, it is possible
  that the order of pages to be freed may end up being negative due to a
  size of zero passed to get_count_order(), and then that negative
  number will cause free_pages() to free a very large section.

  Make sure that does not happen"

* tag 'trace-v5.12-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
  ftrace: Check if pages were allocated before calling free_pages()
This commit is contained in:
Linus Torvalds 2021-03-31 10:14:55 -07:00
commit d19cc4bfbf
1 changed files with 6 additions and 3 deletions
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9
kernel/trace/ftrace.c
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@ -3231,7 +3231,8 @@ ftrace_allocate_pages(unsigned long num_to_init)
pg = start_pg;
while (pg) {
order = get_count_order(pg->size / ENTRIES_PER_PAGE);
free_pages((unsigned long)pg->records, order);
if (order >= 0)
free_pages((unsigned long)pg->records, order);
start_pg = pg->next;
kfree(pg);
pg = start_pg;
@ -6451,7 +6452,8 @@ void ftrace_release_mod(struct module *mod)
clear_mod_from_hashes(pg);
order = get_count_order(pg->size / ENTRIES_PER_PAGE);
free_pages((unsigned long)pg->records, order);
if (order >= 0)
free_pages((unsigned long)pg->records, order);
tmp_page = pg->next;
kfree(pg);
ftrace_number_of_pages -= 1 << order;
@ -6811,7 +6813,8 @@ void ftrace_free_mem(struct module *mod, void *start_ptr, void *end_ptr)
if (!pg->index) {
*last_pg = pg->next;
order = get_count_order(pg->size / ENTRIES_PER_PAGE);
free_pages((unsigned long)pg->records, order);
if (order >= 0)
free_pages((unsigned long)pg->records, order);
ftrace_number_of_pages -= 1 << order;
ftrace_number_of_groups--;
kfree(pg);