| Message ID | 20250411004203.2932899-1-lizhi.xu@windriver.com |
|---|---|
| State | New |
| Headers | show |
| Series | software node: Prevent link creation failure from causing kobj reference count imbalance | expand |
On Fri, Apr 11, 2025 at 08:42:02AM +0800, Lizhi Xu wrote: > syzbot reported a uaf in software_node_notify_remove. [1] > > When any of the two sysfs_create_link() in software_node_notify() fails, > the swnode->kobj reference count will not increase normally, which will > cause swnode to be released incorrectly due to the imbalance of kobj reference > count when executing software_node_notify_remove(). > > Increase the reference count of kobj before creating the link to avoid uaf. > > [1] Please, reduce this to ~5-7 lines only. This is how Submitting Patches document recommends to put backtraces in the commit messages: https://www.kernel.org/doc/html/latest/process/submitting-patches.html#backtraces-in-commit-messages > Fixes: 9eb59204d519 ("iommufd/selftest: Add set_dev_pasid in mock iommu") > Reported-by: syzbot+2ff22910687ee0dfd48e@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=2ff22910687ee0dfd48e > Tested-by: syzbot+2ff22910687ee0dfd48e@syzkaller.appspotmail.com Where is the positive result of it? I can't find the respective log. To me this one https://syzkaller.appspot.com/x/report.txt?x=158af070580000 doesn't sound as a useful report as I don't know if this patch fixes one regression and introduced another. Dmitry?
diff --git a/drivers/base/swnode.c b/drivers/base/swnode.c index b1726a3515f6..5c78fa6ae772 100644 --- a/drivers/base/swnode.c +++ b/drivers/base/swnode.c @@ -1080,6 +1080,7 @@ void software_node_notify(struct device *dev) if (!swnode) return; + kobject_get(&swnode->kobj); ret = sysfs_create_link(&dev->kobj, &swnode->kobj, "software_node"); if (ret) return; @@ -1089,8 +1090,6 @@ void software_node_notify(struct device *dev) sysfs_remove_link(&dev->kobj, "software_node"); return; } - - kobject_get(&swnode->kobj); } void software_node_notify_remove(struct device *dev)
syzbot reported a uaf in software_node_notify_remove. [1] When any of the two sysfs_create_link() in software_node_notify() fails, the swnode->kobj reference count will not increase normally, which will cause swnode to be released incorrectly due to the imbalance of kobj reference count when executing software_node_notify_remove(). Increase the reference count of kobj before creating the link to avoid uaf. [1] BUG: KASAN: slab-use-after-free in software_node_notify_remove+0x1bc/0x1c0 drivers/base/swnode.c:1108 Read of size 1 at addr ffff888033c08908 by task syz-executor105/5844 CPU: 0 UID: 0 PID: 5844 Comm: syz-executor105 Not tainted 6.14.0-syzkaller-12456-gacc4d5ff0b61 #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025 Call Trace: <TASK> __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:408 [inline] print_report+0x16e/0x5b0 mm/kasan/report.c:521 kasan_report+0x143/0x180 mm/kasan/report.c:634 software_node_notify_remove+0x1bc/0x1c0 drivers/base/swnode.c:1108 device_platform_notify_remove drivers/base/core.c:2387 [inline] device_del+0x594/0x9b0 drivers/base/core.c:3858 device_unregister+0x20/0xc0 drivers/base/core.c:3896 mock_dev_destroy drivers/iommu/iommufd/selftest.c:960 [inline] iommufd_test_mock_domain drivers/iommu/iommufd/selftest.c:1022 [inline] iommufd_test+0x3715/0x56a0 drivers/iommu/iommufd/selftest.c:1866 iommufd_fops_ioctl+0x4fc/0x610 drivers/iommu/iommufd/main.c:419 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:906 [inline] __se_sys_ioctl+0xf1/0x160 fs/ioctl.c:892 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f14c7b0b6e9 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 a1 1a 00 00 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 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fff388f87b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007fff388f87d0 RCX: 00007f14c7b0b6e9 RDX: 0000200000000200 RSI: 0000000000003ba0 RDI: 0000000000000003 RBP: 0000000000000002 R08: 00007fff388f8556 R09: 00000000000000a0 R10: 0000000000000002 R11: 0000000000000246 R12: 00007fff388f87cc R13: 431bde82d7b634db R14: 0000000000000001 R15: 0000000000000001 </TASK> Allocated by task 5844: kasan_save_stack mm/kasan/common.c:47 [inline] kasan_save_track+0x3f/0x80 mm/kasan/common.c:68 poison_kmalloc_redzone mm/kasan/common.c:377 [inline] __kasan_kmalloc+0x9d/0xb0 mm/kasan/common.c:394 kasan_kmalloc include/linux/kasan.h:260 [inline] __kmalloc_cache_noprof+0x236/0x370 mm/slub.c:4362 kmalloc_noprof include/linux/slab.h:905 [inline] kzalloc_noprof include/linux/slab.h:1039 [inline] swnode_register+0x5a/0x540 drivers/base/swnode.c:790 fwnode_create_software_node+0x199/0x1f0 drivers/base/swnode.c:949 device_create_managed_software_node+0xd5/0x1f0 drivers/base/swnode.c:1060 mock_dev_create drivers/iommu/iommufd/selftest.c:942 [inline] iommufd_test_mock_domain drivers/iommu/iommufd/selftest.c:989 [inline] iommufd_test+0x3335/0x56a0 drivers/iommu/iommufd/selftest.c:1866 iommufd_fops_ioctl+0x4fc/0x610 drivers/iommu/iommufd/main.c:419 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:906 [inline] __se_sys_ioctl+0xf1/0x160 fs/ioctl.c:892 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Freed by task 5844: kasan_save_stack mm/kasan/common.c:47 [inline] kasan_save_track+0x3f/0x80 mm/kasan/common.c:68 kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:576 poison_slab_object mm/kasan/common.c:247 [inline] __kasan_slab_free+0x59/0x70 mm/kasan/common.c:264 kasan_slab_free include/linux/kasan.h:233 [inline] slab_free_hook mm/slub.c:2389 [inline] slab_free mm/slub.c:4646 [inline] kfree+0x198/0x430 mm/slub.c:4845 kobject_cleanup lib/kobject.c:689 [inline] kobject_release lib/kobject.c:720 [inline] kref_put include/linux/kref.h:65 [inline] kobject_put+0x22f/0x480 lib/kobject.c:737 software_node_notify_remove+0x159/0x1c0 drivers/base/swnode.c:1106 device_platform_notify_remove drivers/base/core.c:2387 [inline] device_del+0x594/0x9b0 drivers/base/core.c:3858 device_unregister+0x20/0xc0 drivers/base/core.c:3896 mock_dev_destroy drivers/iommu/iommufd/selftest.c:960 [inline] iommufd_test_mock_domain drivers/iommu/iommufd/selftest.c:1022 [inline] iommufd_test+0x3715/0x56a0 drivers/iommu/iommufd/selftest.c:1866 iommufd_fops_ioctl+0x4fc/0x610 drivers/iommu/iommufd/main.c:419 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:906 [inline] __se_sys_ioctl+0xf1/0x160 fs/ioctl.c:892 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Fixes: 9eb59204d519 ("iommufd/selftest: Add set_dev_pasid in mock iommu") Reported-by: syzbot+2ff22910687ee0dfd48e@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=2ff22910687ee0dfd48e Tested-by: syzbot+2ff22910687ee0dfd48e@syzkaller.appspotmail.com Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com> --- drivers/base/swnode.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)