[PATCH 5.18 266/879] fbdev: defio: fix the pagelist corruption

Greg Kroah-Hartman
2022-06-07T22:31:58Z

From: Chuansheng Liu <chuansheng.liu@intel.com>

[ Upstream commit 856082f021a28221db2c32bd0531614a8382be67 ]

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: 105a940416fc ("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
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/video/fbdev/core/fb_defio.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/core/fb_defio.c b/drivers/video/fbdev/core/fb_defio.c
index 842c66b3e33d..6aaf6d0abf39 100644
--- a/drivers/video/fbdev/core/fb_defio.c
+++ b/drivers/video/fbdev/core/fb_defio.c
@@ -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;
@@ -213,6 +212,8 @@ 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);
@@ -220,6 +221,12 @@ 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);

--
2.35.1