| From 0af778269a522c988ef0b4188556aba97fb420cc Mon Sep 17 00:00:00 2001 |
| From: Zhen Lei <thunder.leizhen@huawei.com> |
| Date: Mon, 12 Jul 2021 16:55:44 +0800 |
| Subject: fbmem: Do not delete the mode that is still in use |
| |
| From: Zhen Lei <thunder.leizhen@huawei.com> |
| |
| commit 0af778269a522c988ef0b4188556aba97fb420cc upstream. |
| |
| 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> |
| Cc: <stable@vger.kernel.org> # v5.3+ |
| Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> |
| Link: https://patchwork.freedesktop.org/patch/msgid/20210712085544.2828-1-thunder.leizhen@huawei.com |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| drivers/video/fbdev/core/fbmem.c | 12 +++++------- |
| 1 file changed, 5 insertions(+), 7 deletions(-) |
| |
| --- 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_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; |
| } |