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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)

Signed-off-by: Chuansheng Liu <chuansheng.liu@intel.com>
Fixes: 105a940416 ("fbdev/defio: Early-out if page is already enlisted")
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20220318005003.51810-1-chuansheng.liu@intel.com
This commit is contained in:
Chuansheng Liu 2022-03-18 08:50:03 +08:00 committed by Thomas Zimmermann
parent 9f493fd71d
commit 856082f021
1 changed files with 8 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
drivers/video/fbdev/core/fb_defio.c
View File

@ -59,7 +59,6 @@ static vm_fault_t fb_deferred_io_fault(struct vm_fault *vmf)
printk(KERN_ERR "no mapping available\n");
BUG_ON(!page->mapping);
INIT_LIST_HEAD(&page->lru);
page->index = vmf->pgoff;
vmf->page = page;
@ -220,6 +219,8 @@ static void fb_deferred_io_work(struct work_struct *work)
void fb_deferred_io_init(struct fb_info *info)
{
struct fb_deferred_io *fbdefio = info->fbdefio;
struct page *page;
unsigned int i;
BUG_ON(!fbdefio);
mutex_init(&fbdefio->lock);
@ -227,6 +228,12 @@ void fb_deferred_io_init(struct fb_info *info)
INIT_LIST_HEAD(&fbdefio->pagelist);
if (fbdefio->delay == 0) /* set a default of 1 s */
fbdefio->delay = HZ;
/* initialize all the page lists one time */
for (i = 0; i < info->fix.smem_len; i += PAGE_SIZE) {
page = fb_deferred_io_page(info, i);
INIT_LIST_HEAD(&page->lru);
}
}
EXPORT_SYMBOL_GPL(fb_deferred_io_init);