All of lore.kernel.org
 help / color / mirror / Atom feed
From: Hillf Danton <hdanton@sina.com>
To: syzbot <syzbot+f11cda116c57db68c227@syzkaller.appspotmail.com>
Cc: linux-fbdev@vger.kernel.org, b.zolnierkie@samsung.com,
	daniel.vetter@ffwll.ch, mojha@codeaurora.org,
	shile.zhang@linux.alibaba.com, syzkaller-bugs@googlegroups.com,
	linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
	Hillf Danton <hdanton@sina.com>
Subject: Re: KASAN: use-after-free Read in fb_mode_is_equal
Date: Sat,  7 Dec 2019 19:11:35 +0800	[thread overview]
Message-ID: <20191207111135.23312-1-hdanton@sina.com> (raw)


On Sat, 07 Dec 2019 02:05:08 -0800
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    7ada90eb Merge tag 'drm-next-2019-12-06' of git://anongit...
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=16997c82e00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=f07a23020fd7d21a
> dashboard link: https://syzkaller.appspot.com/bug?extid=f11cda116c57db68c227
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> 
> Unfortunately, I don't have any reproducer for this crash yet.
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+f11cda116c57db68c227@syzkaller.appspotmail.com
> 
> ==================================================================
> BUG: KASAN: use-after-free in fb_mode_is_equal+0x297/0x300  
> drivers/video/fbdev/core/modedb.c:924
> Read of size 4 at addr ffff8880992d5d9c by task syz-executor.0/32283
> 
> CPU: 0 PID: 32283 Comm: syz-executor.0 Not tainted 5.4.0-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
> Google 01/01/2011
> Call Trace:
>   __dump_stack lib/dump_stack.c:77 [inline]
>   dump_stack+0x197/0x210 lib/dump_stack.c:118
>   print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374
>   __kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506
>   kasan_report+0x12/0x20 mm/kasan/common.c:639
>   __asan_report_load4_noabort+0x14/0x20 mm/kasan/generic_report.c:134
>   fb_mode_is_equal+0x297/0x300 drivers/video/fbdev/core/modedb.c:924
>   fbcon_mode_deleted+0x12c/0x190 drivers/video/fbdev/core/fbcon.c:3060
>   fb_set_var+0xab9/0xdd0 drivers/video/fbdev/core/fbmem.c:971
>   do_fb_ioctl+0x390/0x7d0 drivers/video/fbdev/core/fbmem.c:1104
>   fb_ioctl+0xe6/0x130 drivers/video/fbdev/core/fbmem.c:1180
>   vfs_ioctl fs/ioctl.c:47 [inline]
>   file_ioctl fs/ioctl.c:545 [inline]
>   do_vfs_ioctl+0x977/0x14e0 fs/ioctl.c:732
>   ksys_ioctl+0xab/0xd0 fs/ioctl.c:749
>   __do_sys_ioctl fs/ioctl.c:756 [inline]
>   __se_sys_ioctl fs/ioctl.c:754 [inline]
>   __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:754
>   do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x45a6f9
> Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007f7aefd54c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045a6f9
> RDX: 0000000020000000 RSI: 0000000000004601 RDI: 0000000000000003
> RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00007f7aefd556d4
> R13: 00000000004c2ef7 R14: 00000000004d8138 R15: 00000000ffffffff
> 
> Allocated by task 9205:
>   save_stack+0x23/0x90 mm/kasan/common.c:72
>   set_track mm/kasan/common.c:80 [inline]
>   __kasan_kmalloc mm/kasan/common.c:513 [inline]
>   __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:486
>   kasan_kmalloc+0x9/0x10 mm/kasan/common.c:527
>   kmem_cache_alloc_trace+0x158/0x790 mm/slab.c:3551
>   kmalloc include/linux/slab.h:556 [inline]
>   fb_add_videomode drivers/video/fbdev/core/modedb.c:1073 [inline]
>   fb_add_videomode+0x2fb/0x610 drivers/video/fbdev/core/modedb.c:1057
>   fb_set_var+0x5ef/0xdd0 drivers/video/fbdev/core/fbmem.c:1041
>   do_fb_ioctl+0x390/0x7d0 drivers/video/fbdev/core/fbmem.c:1104
>   fb_ioctl+0xe6/0x130 drivers/video/fbdev/core/fbmem.c:1180
>   vfs_ioctl fs/ioctl.c:47 [inline]
>   file_ioctl fs/ioctl.c:545 [inline]
>   do_vfs_ioctl+0x977/0x14e0 fs/ioctl.c:732
>   ksys_ioctl+0xab/0xd0 fs/ioctl.c:749
>   __do_sys_ioctl fs/ioctl.c:756 [inline]
>   __se_sys_ioctl fs/ioctl.c:754 [inline]
>   __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:754
>   do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> Freed by task 32276:
>   save_stack+0x23/0x90 mm/kasan/common.c:72
>   set_track mm/kasan/common.c:80 [inline]
>   kasan_set_free_info mm/kasan/common.c:335 [inline]
>   __kasan_slab_free+0x102/0x150 mm/kasan/common.c:474
>   kasan_slab_free+0xe/0x10 mm/kasan/common.c:483
>   __cache_free mm/slab.c:3426 [inline]
>   kfree+0x10a/0x2c0 mm/slab.c:3757
>   fb_delete_videomode+0x3fa/0x540 drivers/video/fbdev/core/modedb.c:1104
>   fb_set_var+0xac8/0xdd0 drivers/video/fbdev/core/fbmem.c:974
>   do_fb_ioctl+0x390/0x7d0 drivers/video/fbdev/core/fbmem.c:1104
>   fb_ioctl+0xe6/0x130 drivers/video/fbdev/core/fbmem.c:1180
>   vfs_ioctl fs/ioctl.c:47 [inline]
>   file_ioctl fs/ioctl.c:545 [inline]
>   do_vfs_ioctl+0x977/0x14e0 fs/ioctl.c:732
>   ksys_ioctl+0xab/0xd0 fs/ioctl.c:749
>   __do_sys_ioctl fs/ioctl.c:756 [inline]
>   __se_sys_ioctl fs/ioctl.c:754 [inline]
>   __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:754
>   do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> The buggy address belongs to the object at ffff8880992d5d80
>   which belongs to the cache kmalloc-96 of size 96
> The buggy address is located 28 bytes inside of
>   96-byte region [ffff8880992d5d80, ffff8880992d5de0)
> The buggy address belongs to the page:
> page:ffffea000264b540 refcount:1 mapcount:0 mapping:ffff8880aa400540  
> index:0x0
> raw: 00fffe0000000200 ffffea00025470c8 ffffea0002992508 ffff8880aa400540
> raw: 0000000000000000 ffff8880992d5000 0000000100000020 0000000000000000
> page dumped because: kasan: bad access detected
> 
> Memory state around the buggy address:
>   ffff8880992d5c80: 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc
>   ffff8880992d5d00: 00 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc
> > ffff8880992d5d80: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
>                              ^
>   ffff8880992d5e00: 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc
>   ffff8880992d5e80: 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc
> ==================================================================

Reset mode that will be deleted to avoid UAF.

--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c
@@ -3058,6 +3058,7 @@ int fbcon_mode_deleted(struct fb_info *i
 		if (!p || !p->mode)
 			continue;
 		if (fb_mode_is_equal(p->mode, mode)) {
+			p->mode = NULL;
 			found = 1;
 			break;
 		}

_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

             reply	other threads:[~2019-12-09  9:46 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-07 11:11 Hillf Danton [this message]
  -- strict thread matches above, loose matches on Subject: below --
2019-12-07 10:05 KASAN: use-after-free Read in fb_mode_is_equal syzbot
2019-12-07 10:05 ` syzbot
2019-12-07 10:05 ` syzbot
2019-12-25  8:17 ` syzbot
2019-12-25  8:17   ` syzbot
2019-12-25  8:17   ` syzbot
2019-12-25 15:26 ` syzbot
2019-12-25 15:26   ` syzbot
2019-12-25 15:26   ` syzbot

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20191207111135.23312-1-hdanton@sina.com \
    --to=hdanton@sina.com \
    --cc=b.zolnierkie@samsung.com \
    --cc=daniel.vetter@ffwll.ch \
    --cc=dri-devel@lists.freedesktop.org \
    --cc=linux-fbdev@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mojha@codeaurora.org \
    --cc=shile.zhang@linux.alibaba.com \
    --cc=syzbot+f11cda116c57db68c227@syzkaller.appspotmail.com \
    --cc=syzkaller-bugs@googlegroups.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.