Messages in this thread | | | Subject | Re: [PATCH] vgacon: Fix an out-of-bounds in vgacon_scrollback_update() | From | Yang Yingliang <> | Date | Thu, 30 Jul 2020 21:24:04 +0800 |
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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.
Thanks,
Yang
> >> vgacon_scrollback_cur->cnt++; >> - p += c->vc_size_row; >> - vgacon_scrollback_cur->tail += c->vc_size_row; >> + p += size; >> + vgacon_scrollback_cur->tail += size; >> >> if (vgacon_scrollback_cur->tail >= vgacon_scrollback_cur->size) >> vgacon_scrollback_cur->tail = 0; >> > thanks,
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