On 30. 07. 20, 15:24, Yang Yingliang wrote:
On 2020/7/30 19:04, Jiri Slaby wrote:
On 13. 07. 20, 12:57, Yang Yingliang wrote:
I got a slab-out-of-bounds report when I doing fuzz test.
[ 334.989515]
[ 334.989577] BUG: KASAN: slab-out-of-bounds in vgacon_scroll+0x57a/0x8ed [ 334.989588] Write of size 1766 at addr ffff8883de69ff3e by task test/2658 [ 334.989593] [ 334.989608] CPU: 3 PID: 2658 Comm: test Not tainted 5.7.0-rc5-00005-g152036d1379f #789 [ 334.989617] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org 04/01/2014 [ 334.989624] Call Trace: [ 334.989646] dump_stack+0xe4/0x14e [ 334.989676] print_address_description.constprop.5+0x3f/0x60 [ 334.989699] ? vgacon_scroll+0x57a/0x8ed [ 334.989710] __kasan_report.cold.8+0x92/0xaf [ 334.989735] ? vgacon_scroll+0x57a/0x8ed [ 334.989761] kasan_report+0x37/0x50 [ 334.989789] check_memory_region+0x1c1/0x1e0 [ 334.989806] memcpy+0x38/0x60 [ 334.989824] vgacon_scroll+0x57a/0x8ed [ 334.989876] con_scroll+0x4ef/0x5e0
...
Because vgacon_scrollback_cur->tail plus memcpy size is greater than vgacon_scrollback_cur->size. Fix this by checking the memcpy size.
Reported-by: Hulk Robot hulkci@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com
drivers/video/console/vgacon.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c index 998b0de1812f..b51ffb9a208d 100644 --- a/drivers/video/console/vgacon.c +++ b/drivers/video/console/vgacon.c @@ -243,6 +243,7 @@ static void vgacon_scrollback_startup(void) static void vgacon_scrollback_update(struct vc_data *c, int t, int count) { void *p; + int size; if (!vgacon_scrollback_cur->data || !vgacon_scrollback_cur->size || c->vc_num != fg_console) @@ -251,13 +252,17 @@ static void vgacon_scrollback_update(struct vc_data *c, int t, int count) p = (void *) (c->vc_origin + t * c->vc_size_row); while (count--) { + size = vgacon_scrollback_cur->size - vgacon_scrollback_cur->tail; + if (size > c->vc_size_row) + size = c->vc_size_row;
scr_memcpyw(vgacon_scrollback_cur->data + vgacon_scrollback_cur->tail, - p, c->vc_size_row); + p, size);
Are you sure the consumer can handle split lines? As vgacon_scrolldelta (soff in particular) looks to me like it doesn't.
Have you tested you patch? I mean with soft scrollback on the vga console?
I only test the patch with the reproduce program.
Out of curiosity, what is it doing? Resize and then scroll by \n (line feed)? Can you share it?
thanks,