From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: gregkh@linuxfoundation.org, jirislaby@kernel.org
Cc: syzbot <syzbot+b308f5fd049fbbc6e74f@syzkaller.appspotmail.com>,
linux-fbdev@vger.kernel.org, b.zolnierkie@samsung.com,
daniel.vetter@ffwll.ch, deller@gmx.de,
syzkaller-bugs@googlegroups.com, linux-kernel@vger.kernel.org,
dri-devel@lists.freedesktop.org,
George Kennedy <george.kennedy@oracle.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Peilin Ye <yepeilin.cs@gmail.com>
Subject: [PATCH] vt_ioctl: make VT_RESIZEX behave like VT_RESIZE
Date: Sun, 27 Sep 2020 11:46:30 +0000 [thread overview]
Message-ID: <4933b81b-9b1a-355b-df0e-9b31e8280ab9@i-love.sakura.ne.jp> (raw)
In-Reply-To: <20200927092701.GA1037755@PWN>
syzbot is reporting UAF/OOB read at bit_putcs()/soft_cursor() [1][2], for
vt_resizex() from ioctl(VT_RESIZEX) allows setting font height larger than
actual font height calculated by con_font_set() from ioctl(PIO_FONT).
Since fbcon_set_font() from con_font_set() allocates minimal amount of
memory based on actual font height calculated by con_font_set(),
use of vt_resizex() can cause UAF/OOB read for font data.
VT_RESIZEX was introduced in Linux 1.3.3, but it is unclear that what
comes to the "+ more" part, and I couldn't find a user of VT_RESIZEX.
#define VT_RESIZE 0x5609 /* set kernel's idea of screensize */
#define VT_RESIZEX 0x560A /* set kernel's idea of screensize + more */
So far we are not aware of syzbot reports caused by setting non-zero value
to v_vlin parameter. But given that it is possible that nobody is using
VT_RESIZEX, we can try removing support for v_clin and v_vlin parameters.
Therefore, this patch effectively makes VT_RESIZEX behave like VT_RESIZE,
with emitting a message if somebody is still using v_clin and/or v_vlin
parameters.
[1] https://syzkaller.appspot.com/bug?id2577e96d88447ded2d3b76d71254fb855245837
[2] https://syzkaller.appspot.com/bug?idk8355d27b2b94fb5cedf4655e3a59162d9e48e3
Reported-by: syzbot <syzbot+b308f5fd049fbbc6e74f@syzkaller.appspotmail.com>
Reported-by: syzbot <syzbot+16469b5e8e5a72e9131e@syzkaller.appspotmail.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
---
drivers/tty/vt/vt_ioctl.c | 57 +++++++--------------------------------
1 file changed, 10 insertions(+), 47 deletions(-)
diff --git a/drivers/tty/vt/vt_ioctl.c b/drivers/tty/vt/vt_ioctl.c
index a4e520bdd521..bc33938e2f20 100644
--- a/drivers/tty/vt/vt_ioctl.c
+++ b/drivers/tty/vt/vt_ioctl.c
@@ -773,58 +773,21 @@ static int vt_resizex(struct vc_data *vc, struct vt_consize __user *cs)
if (copy_from_user(&v, cs, sizeof(struct vt_consize)))
return -EFAULT;
- /* FIXME: Should check the copies properly */
- if (!v.v_vlin)
- v.v_vlin = vc->vc_scan_lines;
-
- if (v.v_clin) {
- int rows = v.v_vlin / v.v_clin;
- if (v.v_rows != rows) {
- if (v.v_rows) /* Parameters don't add up */
- return -EINVAL;
- v.v_rows = rows;
- }
- }
-
- if (v.v_vcol && v.v_ccol) {
- int cols = v.v_vcol / v.v_ccol;
- if (v.v_cols != cols) {
- if (v.v_cols)
- return -EINVAL;
- v.v_cols = cols;
- }
- }
-
- if (v.v_clin > 32)
- return -EINVAL;
+ if (v.v_vlin)
+ pr_info_once("\"struct vt_consize\"->v_vlin is ignored. Please report if you need this.\n");
+ if (v.v_clin)
+ pr_info_once("\"struct vt_consize\"->v_clin is ignored. Please report if you need this.\n");
+ console_lock();
for (i = 0; i < MAX_NR_CONSOLES; i++) {
- struct vc_data *vcp;
+ vc = vc_cons[i].d;
- if (!vc_cons[i].d)
- continue;
- console_lock();
- vcp = vc_cons[i].d;
- if (vcp) {
- int ret;
- int save_scan_lines = vcp->vc_scan_lines;
- int save_font_height = vcp->vc_font.height;
-
- if (v.v_vlin)
- vcp->vc_scan_lines = v.v_vlin;
- if (v.v_clin)
- vcp->vc_font.height = v.v_clin;
- vcp->vc_resize_user = 1;
- ret = vc_resize(vcp, v.v_cols, v.v_rows);
- if (ret) {
- vcp->vc_scan_lines = save_scan_lines;
- vcp->vc_font.height = save_font_height;
- console_unlock();
- return ret;
- }
+ if (vc) {
+ vc->vc_resize_user = 1;
+ vc_resize(vc, v.v_cols, v.v_rows);
}
- console_unlock();
}
+ console_unlock();
return 0;
}
--
2.25.1
next prev parent reply other threads:[~2020-09-27 11:46 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-23 17:30 KASAN: use-after-free Read in bit_putcs syzbot
2020-09-26 2:03 ` syzbot
2020-09-26 16:25 ` Tetsuo Handa
2020-09-26 19:39 ` Peilin Ye
2020-09-27 0:25 ` Tetsuo Handa
2020-09-27 8:28 ` Tetsuo Handa
2020-09-27 9:27 ` Peilin Ye
2020-09-27 11:46 ` Tetsuo Handa [this message]
2020-09-27 12:06 ` [PATCH] vt_ioctl: make VT_RESIZEX behave like VT_RESIZE Greg KH
2020-09-28 17:59 ` Martin Hostettler
2020-09-29 1:12 ` Tetsuo Handa
2020-09-29 10:52 ` Martin Hostettler
2020-09-29 16:56 ` Daniel Vetter
2020-09-29 17:10 ` Greg KH
2021-04-11 21:43 ` Maciej W. Rozycki
2021-04-11 22:15 ` Linus Torvalds
2021-04-12 7:01 ` Daniel Vetter
2021-04-12 13:30 ` Maciej W. Rozycki
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