From: Zhen Lei <thunder.leizhen@huawei.com>
To: Daniel Vetter <daniel.vetter@ffwll.ch>,
Sam Ravnborg <sam@ravnborg.org>,
dri-devel <dri-devel@lists.freedesktop.org>,
linux-fbdev <linux-fbdev@vger.kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>
Cc: Zhen Lei <thunder.leizhen@huawei.com>,
Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Subject: [PATCH 1/1] fbmem: Do not delete the mode that is still in use
Date: Mon, 12 Jul 2021 16:55:44 +0800 [thread overview]
Message-ID: <20210712085544.2828-1-thunder.leizhen@huawei.com> (raw)
The execution of fb_delete_videomode() is not based on the result of the
previous fbcon_mode_deleted(). As a result, the mode is directly deleted,
regardless of whether it is still in use, which may cause UAF.
==================================================================
BUG: KASAN: use-after-free in fb_mode_is_equal+0x36e/0x5e0 \
drivers/video/fbdev/core/modedb.c:924
Read of size 4 at addr ffff88807e0ddb1c by task syz-executor.0/18962
CPU: 2 PID: 18962 Comm: syz-executor.0 Not tainted 5.10.45-rc1+ #3
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ...
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x137/0x1be lib/dump_stack.c:118
print_address_description+0x6c/0x640 mm/kasan/report.c:385
__kasan_report mm/kasan/report.c:545 [inline]
kasan_report+0x13d/0x1e0 mm/kasan/report.c:562
fb_mode_is_equal+0x36e/0x5e0 drivers/video/fbdev/core/modedb.c:924
fbcon_mode_deleted+0x16a/0x220 drivers/video/fbdev/core/fbcon.c:2746
fb_set_var+0x1e1/0xdb0 drivers/video/fbdev/core/fbmem.c:975
do_fb_ioctl+0x4d9/0x6e0 drivers/video/fbdev/core/fbmem.c:1108
vfs_ioctl fs/ioctl.c:48 [inline]
__do_sys_ioctl fs/ioctl.c:753 [inline]
__se_sys_ioctl+0xfb/0x170 fs/ioctl.c:739
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9
Freed by task 18960:
kasan_save_stack mm/kasan/common.c:48 [inline]
kasan_set_track+0x3d/0x70 mm/kasan/common.c:56
kasan_set_free_info+0x17/0x30 mm/kasan/generic.c:355
__kasan_slab_free+0x108/0x140 mm/kasan/common.c:422
slab_free_hook mm/slub.c:1541 [inline]
slab_free_freelist_hook+0xd6/0x1a0 mm/slub.c:1574
slab_free mm/slub.c:3139 [inline]
kfree+0xca/0x3d0 mm/slub.c:4121
fb_delete_videomode+0x56a/0x820 drivers/video/fbdev/core/modedb.c:1104
fb_set_var+0x1f3/0xdb0 drivers/video/fbdev/core/fbmem.c:978
do_fb_ioctl+0x4d9/0x6e0 drivers/video/fbdev/core/fbmem.c:1108
vfs_ioctl fs/ioctl.c:48 [inline]
__do_sys_ioctl fs/ioctl.c:753 [inline]
__se_sys_ioctl+0xfb/0x170 fs/ioctl.c:739
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9
Fixes: 13ff178ccd6d ("fbcon: Call fbcon_mode_deleted/new_modelist directly")
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
---
drivers/video/fbdev/core/fbmem.c | 12 +++++-------
1 file changed, 5 insertions(+), 7 deletions(-)
diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
index 98f193078c05..1c855145711b 100644
--- a/drivers/video/fbdev/core/fbmem.c
+++ b/drivers/video/fbdev/core/fbmem.c
@@ -970,13 +970,11 @@ fb_set_var(struct fb_info *info, struct fb_var_screeninfo *var)
fb_var_to_videomode(&mode2, &info->var);
/* make sure we don't delete the videomode of current var */
ret = fb_mode_is_equal(&mode1, &mode2);
-
- if (!ret)
- fbcon_mode_deleted(info, &mode1);
-
- if (!ret)
- fb_delete_videomode(&mode1, &info->modelist);
-
+ if (!ret) {
+ ret = fbcon_mode_deleted(info, &mode1);
+ if (!ret)
+ fb_delete_videomode(&mode1, &info->modelist);
+ }
return ret ? -EINVAL : 0;
}
--
2.25.1
next reply other threads:[~2021-07-12 9:05 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-12 8:55 Zhen Lei [this message]
2021-07-12 14:37 ` [PATCH 1/1] fbmem: Do not delete the mode that is still in use Daniel Vetter
2021-07-13 11:15 ` Daniel Vetter
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