From: Randy Dunlap <rdunlap@infradead.org>
To: syzbot <syzbot+04168c8063cfdde1db5e@syzkaller.appspotmail.com>,
akpm@linux-foundation.org, b.zolnierkie@samsung.com,
colin.king@canonical.com, dri-devel@lists.freedesktop.org,
linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org,
masahiroy@kernel.org, penguin-kernel@i-love.sakura.ne.jp,
syzkaller-bugs@googlegroups.com
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Subject: Re: [syzbot] BUG: unable to handle kernel paging request in vga16fb_fillrect
Date: Sun, 29 Aug 2021 17:24:50 -0700 [thread overview]
Message-ID: <131b24e5-ee31-6f7b-42b4-c34583711913@infradead.org> (raw)
In-Reply-To: <000000000000815b9605c70e74f8@google.com>
On 7/13/21 10:16 PM, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 3dbdb38e Merge branch 'for-5.14' of git://git.kernel.org/p..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1323c402300000
> kernel config: https://syzkaller.appspot.com/x/.config?x=a1fcf15a09815757
> dashboard link: https://syzkaller.appspot.com/bug?extid=04168c8063cfdde1db5e
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11f0e772300000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1114b9b0300000
Here are the fields that are set in the C reproducer for this ioctl:
#define FBIOPUT_VSCREENINFO 0x4601
*(uint32_t*)0x20000200 = 0x356; // xres: 854
*(uint32_t*)0x20000204 = 8; // yres
*(uint32_t*)0x20000208 = 0x600; // xres_virtual: 1536
*(uint32_t*)0x2000020c = 0x10000000; // yres_virtual: huge
*(uint32_t*)0x20000210 = 0; // xoffset
*(uint32_t*)0x20000214 = 0; // yoffset
*(uint32_t*)0x20000218 = 4; // bits_per_pixel
*(uint32_t*)0x2000021c = 0; // grayscale: false
*(uint32_t*)0x20000220 = 0x3000000; // red bitfield
*(uint32_t*)0x20000224 = 0; // green bitfield
*(uint32_t*)0x20000228 = 0; // blue bitfield
*(uint32_t*)0x2000022c = 0; // transp
*(uint32_t*)0x20000230 = 0; // nonstd: false
*(uint32_t*)0x20000234 = 0; // activate
*(uint32_t*)0x20000238 = 0; // height
*(uint32_t*)0x2000023c = 0; // width
*(uint32_t*)0x20000240 = 0; // accel_flags
*(uint32_t*)0x20000244 = 0; // pixclock
*(uint32_t*)0x20000248 = 0; // left_margin
*(uint32_t*)0x2000024c = 0; // right_margin
*(uint32_t*)0x20000250 = 0; // upper_margin
*(uint32_t*)0x20000254 = 0; // lower_margin
*(uint32_t*)0x20000258 = 0; // hsync_len
*(uint32_t*)0x2000025c = 0; // vsync_len
*(uint32_t*)0x20000260 = 0; // sync
*(uint32_t*)0x20000264 = 0; // vmode
*(uint32_t*)0x20000268 = 0; // rotate
*(uint32_t*)0x2000026c = 0; // colorspace
*(uint32_t*)0x20000270 = 0; // rsvd0
*(uint32_t*)0x20000274 = 0; // rsvd1
*(uint32_t*)0x20000278 = 0; // rsvd2
*(uint32_t*)0x2000027c = 0; // rsvd3
*(uint32_t*)0x20000280 = 0; // notdef...
*(uint32_t*)0x20000284 = 0;
*(uint32_t*)0x20000288 = 0;
*(uint32_t*)0x2000028c = 0;
memset((void*)0x20000290, 0, 16);
syscall(__NR_ioctl, r[0], 0x4601, 0x20000200ul);
Note that yres_virtual is set to 0x10000000. Is there no practical limit
(hence limit check) that can be used here?
Also, in vga16fb_check_var(), beginning at line 404:
404 if (yres > vyres)
405 vyres = yres;
406 if (vxres * vyres > maxmem) {
407 vyres = maxmem / vxres;
408 if (vyres < yres)
409 return -ENOMEM;
410 }
At line 406, the product of vxres * vyres overflows 32 bits (is 0 in this
case/example), so any protection from this block is lost.
But even if yres_virtual (aka vyres) is "only" 0x01000000, so no
multiplication overflow occurs, the resulting value of vyres "seems"
to still be too large and can cause an error [I'm not sure about this
last part -- I need to use a new gcc so that KASAN will work.]
> Bisection is inconclusive: the issue happens on the oldest tested release.
>
> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=10fa45d8300000
> final oops: https://syzkaller.appspot.com/x/report.txt?x=12fa45d8300000
> console output: https://syzkaller.appspot.com/x/log.txt?x=14fa45d8300000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+04168c8063cfdde1db5e@syzkaller.appspotmail.com
>
> BUG: unable to handle page fault for address: ffff888001000050
> #PF: supervisor write access in kernel mode
> #PF: error_code(0x0003) - permissions violation
> PGD 10e01067 P4D 10e01067 PUD 10e02067 PMD 80000000010001e1
> Oops: 0003 [#1] PREEMPT SMP KASAN
> CPU: 1 PID: 8433 Comm: syz-executor067 Tainted: G W 5.13.0-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> RIP: 0010:writeb arch/x86/include/asm/io.h:65 [inline]
> RIP: 0010:vga16fb_fillrect+0x993/0x18d0 drivers/video/fbdev/vga16fb.c:923
> Code: 6c fd 48 63 44 24 10 45 31 f6 48 89 04 24 e8 44 a6 6c fd 31 ff 89 de 31 ed e8 79 ad 6c fd 85 db 4d 89 ec 74 22 e8 2d a6 6c fd <45> 88 34 24 83 c5 01 89 df 49 83 c4 01 89 ee e8 49 ae 6c fd 39 eb
> RSP: 0018:ffffc90000eff848 EFLAGS: 00010293
> RAX: 0000000000000000 RBX: 000000000000001b RCX: 0000000000000000
> RDX: ffff88802d949c40 RSI: ffffffff8408e403 RDI: 0000000000000003
> RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffff8408dd8d
> R10: ffffffff8408e3f7 R11: 0000000000000000 R12: ffff888001000050
> R13: ffff888001000050 R14: 0000000000000000 R15: 000000000ffeb7ff
> FS: 0000000001aa2300(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: ffff888001000050 CR3: 00000000346fb000 CR4: 00000000001506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
> bit_clear_margins+0x3f6/0x4b0 drivers/video/fbdev/core/bitblit.c:224
> fbcon_clear_margins+0x1f1/0x280 drivers/video/fbdev/core/fbcon.c:1315
> fbcon_switch+0xa8c/0x1620 drivers/video/fbdev/core/fbcon.c:2146
> redraw_screen+0x2b9/0x740 drivers/tty/vt/vt.c:1021
> fbcon_modechanged+0x593/0x6d0 drivers/video/fbdev/core/fbcon.c:2651
> fbcon_update_vcs+0x3a/0x50 drivers/video/fbdev/core/fbcon.c:2696
> do_fb_ioctl+0x62e/0x690 drivers/video/fbdev/core/fbmem.c:1110
> fb_ioctl+0xe7/0x150 drivers/video/fbdev/core/fbmem.c:1185
> vfs_ioctl fs/ioctl.c:51 [inline]
> __do_sys_ioctl fs/ioctl.c:1069 [inline]
> __se_sys_ioctl fs/ioctl.c:1055 [inline]
> __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:1055
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x43efd9
> Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffc362df848 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 0000000000400488 RCX: 000000000043efd9
> RDX: 0000000020000200 RSI: 0000000000004601 RDI: 0000000000000003
> RBP: 0000000000402fc0 R08: 0000000000000000 R09: 0000000000400488
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000403050
> R13: 0000000000000000 R14: 00000000004ac018 R15: 0000000000400488
> Modules linked in:
> CR2: ffff888001000050
> ---[ end trace 39dce64bc5621bd3 ]---
> RIP: 0010:writeb arch/x86/include/asm/io.h:65 [inline]
> RIP: 0010:vga16fb_fillrect+0x993/0x18d0 drivers/video/fbdev/vga16fb.c:923
> Code: 6c fd 48 63 44 24 10 45 31 f6 48 89 04 24 e8 44 a6 6c fd 31 ff 89 de 31 ed e8 79 ad 6c fd 85 db 4d 89 ec 74 22 e8 2d a6 6c fd <45> 88 34 24 83 c5 01 89 df 49 83 c4 01 89 ee e8 49 ae 6c fd 39 eb
> RSP: 0018:ffffc90000eff848 EFLAGS: 00010293
> RAX: 0000000000000000 RBX: 000000000000001b RCX: 0000000000000000
> RDX: ffff88802d949c40 RSI: ffffffff8408e403 RDI: 0000000000000003
> RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffff8408dd8d
> R10: ffffffff8408e3f7 R11: 0000000000000000 R12: ffff888001000050
> R13: ffff888001000050 R14: 0000000000000000 R15: 000000000ffeb7ff
> FS: 0000000001aa2300(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: ffff888001000050 CR3: 00000000346fb000 CR4: 00000000001506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
--
~Randy
next prev parent reply other threads:[~2021-08-30 0:25 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 [this message]
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 ` [PATCH v2] " Tetsuo Handa
2021-09-01 7:12 ` 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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