From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: Daniel Vetter <daniel.vetter@ffwll.ch>,
Geert Uytterhoeven <geert@linux-m68k.org>
Cc: syzbot <syzbot+04168c8063cfdde1db5e@syzkaller.appspotmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
Colin King <colin.king@canonical.com>,
DRI Development <dri-devel@lists.freedesktop.org>,
Linux Fbdev development list <linux-fbdev@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Masahiro Yamada <masahiroy@kernel.org>,
syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
Randy Dunlap <rdunlap@infradead.org>
Subject: [PATCH v2] fbmem: don't allow too huge resolutions
Date: Wed, 1 Sep 2021 10:14:43 +0900 [thread overview]
Message-ID: <750ed1ae-de80-b232-4aea-79d60c212fab@i-love.sakura.ne.jp> (raw)
In-Reply-To: <CAKMK7uHuOQWUnsiH00QFbHKgTdjjryK0ra9We2stojXMiAVgJA@mail.gmail.com>
syzbot is reporting page fault at vga16fb_fillrect() [1], for
vga16fb_check_var() is failing to detect multiplication overflow.
if (vxres * vyres > maxmem) {
vyres = maxmem / vxres;
if (vyres < yres)
return -ENOMEM;
}
Since no module would accept too huge resolutions where multiplication
overflow happens, let's reject in the common path.
Link: https://syzkaller.appspot.com/bug?extid=04168c8063cfdde1db5e [1]
Reported-by: syzbot <syzbot+04168c8063cfdde1db5e@syzkaller.appspotmail.com>
Debugged-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
---
Changes in v2:
Use check_mul_overflow(), suggested by Geert Uytterhoeven <geert@linux-m68k.org>.
drivers/video/fbdev/core/fbmem.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
index 1c855145711b..53d23b3d010c 100644
--- a/drivers/video/fbdev/core/fbmem.c
+++ b/drivers/video/fbdev/core/fbmem.c
@@ -962,6 +962,7 @@ fb_set_var(struct fb_info *info, struct fb_var_screeninfo *var)
struct fb_var_screeninfo old_var;
struct fb_videomode mode;
struct fb_event event;
+ u32 unused;
if (var->activate & FB_ACTIVATE_INV_MODE) {
struct fb_videomode mode1, mode2;
@@ -1008,6 +1009,11 @@ fb_set_var(struct fb_info *info, struct fb_var_screeninfo *var)
if (var->xres < 8 || var->yres < 8)
return -EINVAL;
+ /* Too huge resolution causes multiplication overflow. */
+ if (check_mul_overflow(var->xres, var->yres, &unused) ||
+ check_mul_overflow(var->xres_virtual, var->yres_virtual, &unused))
+ return -EINVAL;
+
ret = info->fbops->fb_check_var(var, info);
if (ret)
--
2.25.1
next prev parent reply other threads:[~2021-09-01 1:15 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-14 5:16 [syzbot] BUG: unable to handle kernel paging request in vga16fb_fillrect syzbot
2021-08-30 0:24 ` Randy Dunlap
2021-08-30 2:27 ` Tetsuo Handa
2021-08-30 2:31 ` Randy Dunlap
2021-08-30 16:05 ` [PATCH] fbmem: don't allow too huge resolutions Tetsuo Handa
2021-08-31 6:48 ` Geert Uytterhoeven
2021-08-31 15:23 ` Tetsuo Handa
2021-08-31 16:20 ` Daniel Vetter
2021-08-31 17:19 ` Geert Uytterhoeven
2021-08-31 18:53 ` Daniel Vetter
2021-08-31 18:56 ` Geert Uytterhoeven
2021-08-31 19:04 ` Daniel Vetter
2021-09-01 1:14 ` Tetsuo Handa [this message]
2021-09-01 7:12 ` [PATCH v2] " Geert Uytterhoeven
2021-09-08 10:27 ` [PATCH v2 (repost)] " Tetsuo Handa
2021-09-08 16:52 ` Daniel Vetter
2021-08-30 12:00 ` [syzbot] BUG: unable to handle kernel paging request in vga16fb_fillrect Geert Uytterhoeven
2021-08-30 13:00 ` Dan Carpenter
2021-08-30 13:37 ` Tetsuo Handa
2021-08-30 13:47 ` Dan Carpenter
2021-08-30 14:25 ` Tetsuo Handa
2021-08-30 14:29 ` Dan Carpenter
2021-08-30 14:30 ` Geert Uytterhoeven
2021-08-30 14:38 ` Tetsuo Handa
2021-08-30 14:53 ` Geert Uytterhoeven
2021-08-30 15:00 ` Geert Uytterhoeven
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