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List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6e02:4602:b0:3d3:ce1b:5e84 with SMTP id e9e14a558f8ab-3d3ce1b6053mr8414535ab.22.1740483816347; Tue, 25 Feb 2025 03:43:36 -0800 (PST) Date: Tue, 25 Feb 2025 03:43:36 -0800 In-Reply-To: <67bd6bef.050a0220.bbfd1.009d.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <67bdace8.050a0220.bbfd1.00a6.GAE@google.com> Subject: Re: [syzbot] [fbdev?] KASAN: slab-out-of-bounds Read in fbcon_prepare_logo From: syzbot To: deller@gmx.de, dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org, simona@ffwll.ch, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" syzbot has found a reproducer for the following issue on: HEAD commit: d082ecbc71e9 Linux 6.14-rc4 git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=14f56db0580000 kernel config: https://syzkaller.appspot.com/x/.config?x=b1635bf4c5557b92 dashboard link: https://syzkaller.appspot.com/bug?extid=0c815b25cdb3678e7083 compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=172e77f8580000 Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/323a5d590eec/disk-d082ecbc.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/f7c4b6e33fd9/vmlinux-d082ecbc.xz kernel image: https://storage.googleapis.com/syzbot-assets/c518bbd55334/bzImage-d082ecbc.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+0c815b25cdb3678e7083@syzkaller.appspotmail.com ================================================================== BUG: KASAN: slab-out-of-bounds in scr_memcpyw include/linux/vt_buffer.h:38 [inline] BUG: KASAN: slab-out-of-bounds in fbcon_prepare_logo+0xa15/0xc80 drivers/video/fbdev/core/fbcon.c:614 Read of size 256 at addr ffff888032edef60 by task syz.2.2428/8600 CPU: 0 UID: 0 PID: 8600 Comm: syz.2.2428 Not tainted 6.14.0-rc4-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:408 [inline] print_report+0xc3/0x670 mm/kasan/report.c:521 kasan_report+0xd9/0x110 mm/kasan/report.c:634 check_region_inline mm/kasan/generic.c:183 [inline] kasan_check_range+0xef/0x1a0 mm/kasan/generic.c:189 __asan_memcpy+0x23/0x60 mm/kasan/shadow.c:105 scr_memcpyw include/linux/vt_buffer.h:38 [inline] fbcon_prepare_logo+0xa15/0xc80 drivers/video/fbdev/core/fbcon.c:614 fbcon_init+0xd41/0x1890 drivers/video/fbdev/core/fbcon.c:1146 visual_init+0x31d/0x620 drivers/tty/vt/vt.c:1011 do_bind_con_driver.isra.0+0x57a/0xbf0 drivers/tty/vt/vt.c:3831 vt_bind drivers/tty/vt/vt.c:3987 [inline] store_bind+0x61d/0x760 drivers/tty/vt/vt.c:4059 dev_attr_store+0x55/0x80 drivers/base/core.c:2439 sysfs_kf_write+0x117/0x170 fs/sysfs/file.c:139 kernfs_fop_write_iter+0x33d/0x500 fs/kernfs/file.c:334 new_sync_write fs/read_write.c:586 [inline] vfs_write+0x5ae/0x1150 fs/read_write.c:679 ksys_write+0x12b/0x250 fs/read_write.c:731 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fb44418d169 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffe52f027e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007fb4443a5fa0 RCX: 00007fb44418d169 RDX: 0000000000000002 RSI: 0000000000000000 RDI: 0000000000000003 RBP: 00007fb44420e2a0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fb4443a5fa0 R14: 00007fb4443a5fa0 R15: 0000000000000003 The buggy address belongs to the physical page: page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x32edc head: order:2 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0 flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff) raw: 00fff00000000040 0000000000000000 dead000000000122 0000000000000000 raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000 head: 00fff00000000040 0000000000000000 dead000000000122 0000000000000000 head: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000 head: 00fff00000000002 ffffea0000cbb701 ffffffffffffffff 0000000000000000 head: 0000000000000004 0000000000000000 00000000ffffffff 0000000000000000 page dumped because: kasan: bad access detected page_owner tracks the page as allocated page last allocated via order 2, migratetype Unmovable, gfp_mask 0x140dc0(GFP_USER|__GFP_COMP|__GFP_ZERO), pid 8600, tgid 8600 (syz.2.2428), ts 463971995066, free_ts 463963903452 set_page_owner include/linux/page_owner.h:32 [inline] post_alloc_hook+0x181/0x1b0 mm/page_alloc.c:1551 prep_new_page mm/page_alloc.c:1559 [inline] get_page_from_freelist+0xfce/0x2f80 mm/page_alloc.c:3477 __alloc_frozen_pages_noprof+0x221/0x2470 mm/page_alloc.c:4739 __alloc_pages_noprof+0xb/0x1b0 mm/page_alloc.c:4773 __alloc_pages_node_noprof include/linux/gfp.h:265 [inline] alloc_pages_node_noprof include/linux/gfp.h:292 [inline] ___kmalloc_large_node+0x84/0x1b0 mm/slub.c:4239 __kmalloc_large_node_noprof+0x1c/0x70 mm/slub.c:4266 __do_kmalloc_node mm/slub.c:4282 [inline] __kmalloc_noprof.cold+0xc/0x61 mm/slub.c:4306 kmalloc_noprof include/linux/slab.h:905 [inline] kzalloc_noprof include/linux/slab.h:1037 [inline] vc_do_resize+0x1e3/0x10f0 drivers/tty/vt/vt.c:1174 vc_resize include/linux/vt_kern.h:49 [inline] fbcon_init+0xd1d/0x1890 drivers/video/fbdev/core/fbcon.c:1143 visual_init+0x31d/0x620 drivers/tty/vt/vt.c:1011 do_bind_con_driver.isra.0+0x57a/0xbf0 drivers/tty/vt/vt.c:3831 vt_bind drivers/tty/vt/vt.c:3987 [inline] store_bind+0x61d/0x760 drivers/tty/vt/vt.c:4059 dev_attr_store+0x55/0x80 drivers/base/core.c:2439 sysfs_kf_write+0x117/0x170 fs/sysfs/file.c:139 kernfs_fop_write_iter+0x33d/0x500 fs/kernfs/file.c:334 new_sync_write fs/read_write.c:586 [inline] vfs_write+0x5ae/0x1150 fs/read_write.c:679 page last free pid 8600 tgid 8600 stack trace: reset_page_owner include/linux/page_owner.h:25 [inline] free_pages_prepare mm/page_alloc.c:1127 [inline] free_frozen_pages+0x6db/0xfb0 mm/page_alloc.c:2660 __folio_put+0x32a/0x450 mm/swap.c:112 vc_do_resize+0xe31/0x10f0 drivers/tty/vt/vt.c:1194 vc_resize include/linux/vt_kern.h:49 [inline] fbcon_startup+0x406/0xb70 drivers/video/fbdev/core/fbcon.c:997 do_bind_con_driver.isra.0+0x207/0xbf0 drivers/tty/vt/vt.c:3794 vt_bind drivers/tty/vt/vt.c:3987 [inline] store_bind+0x61d/0x760 drivers/tty/vt/vt.c:4059 dev_attr_store+0x55/0x80 drivers/base/core.c:2439 sysfs_kf_write+0x117/0x170 fs/sysfs/file.c:139 kernfs_fop_write_iter+0x33d/0x500 fs/kernfs/file.c:334 new_sync_write fs/read_write.c:586 [inline] vfs_write+0x5ae/0x1150 fs/read_write.c:679 ksys_write+0x12b/0x250 fs/read_write.c:731 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f Memory state around the buggy address: ffff888032edef00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff888032edef80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 >ffff888032edf000: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe ^ ffff888032edf080: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe ffff888032edf100: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe ================================================================== --- If you want syzbot to run the reproducer, reply with: #syz test: git://repo/address.git branch-or-commit-hash If you attach or paste a git patch, syzbot will apply it before testing.