CVE-2022-49511

In the Linux kernel, the following vulnerability has been resolved:

fbdev: defio: fix the pagelist corruption

Easily hit the below list corruption:

==

list_add corruption. prev->next should be next (ffffffffc0ceb090), but

was ffffec604507edc8. (prev=ffffec604507edc8).

WARNING: CPU: 65 PID: 3959 at lib/list_debug.c:26

__list_add_valid+0x53/0x80

CPU: 65 PID: 3959 Comm: fbdev Tainted: G U

RIP: 0010:__list_add_valid+0x53/0x80

Call Trace:

<TASK>

fb_deferred_io_mkwrite+0xea/0x150

do_page_mkwrite+0x57/0xc0

do_wp_page+0x278/0x2f0

__handle_mm_fault+0xdc2/0x1590

handle_mm_fault+0xdd/0x2c0

do_user_addr_fault+0x1d3/0x650

exc_page_fault+0x77/0x180

? asm_exc_page_fault+0x8/0x30

asm_exc_page_fault+0x1e/0x30

RIP: 0033:0x7fd98fc8fad1

==

Figure out the race happens when one process is adding &page->lru into

the pagelist tail in fb_deferred_io_mkwrite(), another process is

re-initializing the same &page->lru in fb_deferred_io_fault(), which is

not protected by the lock.

This fix is to init all the page lists one time during initialization,

it not only fixes the list corruption, but also avoids INIT_LIST_HEAD()

redundantly.

V2: change "int i" to "unsigned int i" (Geert Uytterhoeven)