On Mon, 28 Mar 2022 12:09:59 +0200, Jiri Slaby wrote:
On 28. 03. 22, 11:35, Xiaomeng Tong wrote:
The bug is here: if (s->len != flen) {
The list iterator 's' will point to a bogus position containing HEAD if the list is empty or no element is found.
Could you also explain how that can happen?
When list_for_each_entry_* do not early exits (if the list is empty or no break/goto/return hit inside the loop), it will set pos ('s' here) with a bogus pointer that point to a invalid struct computed based on &HEAD using container_of.
#define list_for_each_entry(pos, head, member) \ for (pos = list_first_entry(head, typeof(*pos), member); \ !list_entry_is_head(pos, head, member); \ pos = list_next_entry(pos, member))
This case must be checked before any use of the iterator, otherwise it may bpass the 'if (s->len != flen) {' in theory iif s->len's value is flen,
bpass + iif -- others already commented on that and you ignored them.
Thank you, i will correct it.
or/and lead to an invalid memory access.
To fix this bug, use a new variable 'iter' as the list iterator, while using the origin variable 's' as a dedicated pointer to point to the found element. And if the list is empty or no element is found, WARN_ON and return.
Cc: stable@vger.kernel.org Fixes: ^1da177e4c3f4 ("Linux-2.6.12-rc2")
That's barely the commit introducing the behavior.
So just remove the Fixes tag? or something else? I find this commitID with git blame.
-- Xiaomeng Tong