On Sat, Feb 01, 2020 at 12:32:09PM +0800, Hillf Danton wrote:
Fri, 31 Jan 2020 14:28:10 -0800 (PST)
syzbot found the following crash on:
HEAD commit: 39bed42d Merge tag 'for-linus-hmm' of git://git.kernel.org.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=179465bee00000 kernel config: https://syzkaller.appspot.com/x/.config?x=2646535f8818ae25 dashboard link: https://syzkaller.appspot.com/bug?extid=0dc4444774d419e916c8 compiler: gcc (GCC) 9.0.0 20181231 (experimental) syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16251279e00000
The bug was bisected to:
commit 7611750784664db46d0db95631e322aeb263dde7 Author: Alex Deucher alexander.deucher@amd.com Date: Wed Jun 21 16:31:41 2017 +0000
drm/amdgpu: use kernel is_power_of_2 rather than local versionbisection log: https://syzkaller.appspot.com/x/bisect.txt?x=11628df1e00000 final crash: https://syzkaller.appspot.com/x/report.txt?x=13628df1e00000 console output: https://syzkaller.appspot.com/x/log.txt?x=15628df1e00000
IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+0dc4444774d419e916c8@syzkaller.appspotmail.com Fixes: 761175078466 ("drm/amdgpu: use kernel is_power_of_2 rather than local version")
================================================================== BUG: KASAN: use-after-free in vgem_gem_dumb_create+0x238/0x250 drivers/gpu/drm/vgem/vgem_drv.c:221 Read of size 8 at addr ffff88809fa67908 by task syz-executor.0/14871
CPU: 0 PID: 14871 Comm: syz-executor.0 Not tainted 5.5.0-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/0x32 mm/kasan/report.c:506 kasan_report+0x12/0x20 mm/kasan/common.c:639 __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:135 vgem_gem_dumb_create+0x238/0x250 drivers/gpu/drm/vgem/vgem_drv.c:221 drm_mode_create_dumb+0x282/0x310 drivers/gpu/drm/drm_dumb_buffers.c:94 drm_mode_create_dumb_ioctl+0x26/0x30 drivers/gpu/drm/drm_dumb_buffers.c:100 drm_ioctl_kernel+0x244/0x300 drivers/gpu/drm/drm_ioctl.c:786 drm_ioctl+0x54e/0xa60 drivers/gpu/drm/drm_ioctl.c:886 vfs_ioctl fs/ioctl.c:47 [inline] ksys_ioctl+0x123/0x180 fs/ioctl.c:747 __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: 0033:0x45b349 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:00007f871af46c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f871af476d4 RCX: 000000000045b349 RDX: 0000000020000180 RSI: 00000000c02064b2 RDI: 0000000000000003 RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 0000000000000285 R14: 00000000004d14d0 R15: 000000000075bf2c
Allocated by task 14871: 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] kzalloc include/linux/slab.h:670 [inline] __vgem_gem_create+0x49/0x100 drivers/gpu/drm/vgem/vgem_drv.c:165 vgem_gem_create drivers/gpu/drm/vgem/vgem_drv.c:194 [inline] vgem_gem_dumb_create+0xd7/0x250 drivers/gpu/drm/vgem/vgem_drv.c:217 drm_mode_create_dumb+0x282/0x310 drivers/gpu/drm/drm_dumb_buffers.c:94 drm_mode_create_dumb_ioctl+0x26/0x30 drivers/gpu/drm/drm_dumb_buffers.c:100 drm_ioctl_kernel+0x244/0x300 drivers/gpu/drm/drm_ioctl.c:786 drm_ioctl+0x54e/0xa60 drivers/gpu/drm/drm_ioctl.c:886 vfs_ioctl fs/ioctl.c:47 [inline] ksys_ioctl+0x123/0x180 fs/ioctl.c:747 __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 14871: 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 vgem_gem_free_object+0xbe/0xe0 drivers/gpu/drm/vgem/vgem_drv.c:68 drm_gem_object_free+0x100/0x220 drivers/gpu/drm/drm_gem.c:983 kref_put include/linux/kref.h:65 [inline] drm_gem_object_put_unlocked drivers/gpu/drm/drm_gem.c:1017 [inline] drm_gem_object_put_unlocked+0x196/0x1c0 drivers/gpu/drm/drm_gem.c:1002 vgem_gem_create drivers/gpu/drm/vgem/vgem_drv.c:199 [inline] vgem_gem_dumb_create+0x115/0x250 drivers/gpu/drm/vgem/vgem_drv.c:217 drm_mode_create_dumb+0x282/0x310 drivers/gpu/drm/drm_dumb_buffers.c:94 drm_mode_create_dumb_ioctl+0x26/0x30 drivers/gpu/drm/drm_dumb_buffers.c:100 drm_ioctl_kernel+0x244/0x300 drivers/gpu/drm/drm_ioctl.c:786 drm_ioctl+0x54e/0xa60 drivers/gpu/drm/drm_ioctl.c:886 vfs_ioctl fs/ioctl.c:47 [inline] ksys_ioctl+0x123/0x180 fs/ioctl.c:747 __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 ffff88809fa67800 which belongs to the cache kmalloc-1k of size 1024 The buggy address is located 264 bytes inside of 1024-byte region [ffff88809fa67800, ffff88809fa67c00) The buggy address belongs to the page: page:ffffea00027e99c0 refcount:1 mapcount:0 mapping:ffff8880aa400c40 index:0x0 raw: 00fffe0000000200 ffffea0002293548 ffffea00023e1f08 ffff8880aa400c40 raw: 0000000000000000 ffff88809fa67000 0000000100000002 0000000000000000 page dumped because: kasan: bad access detected
Memory state around the buggy address: ffff88809fa67800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88809fa67880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88809fa67900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^ffff88809fa67980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88809fa67a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================
Release obj in error path.
--- a/drivers/gpu/drm/vgem/vgem_drv.c +++ b/drivers/gpu/drm/vgem/vgem_drv.c @@ -196,10 +196,10 @@ static struct drm_gem_object *vgem_gem_c return ERR_CAST(obj); ret = drm_gem_handle_create(file, &obj->base, handle);
- drm_gem_object_put_unlocked(&obj->base);
- if (ret)
- if (ret) {
drm_gem_object_put_unlocked(&obj->base);
- } return &obj->base;
Oh yeah. It's weird that we never noticed the success path was broken. It's been that way for three years and no one noticed at all. Very strange.
Anyway, it already gets freed on error in drm_gem_handle_create() so we should just delete the drm_gem_object_put_unlocked() here it looks like.
regards, dan carpenter