Messages in this thread Patch in this message | | | From | Chen Zhongjin <> | Subject | [PATCH] firmware: dmi-sysfs: Fix null-ptr-deref in dmi_sysfs_register_handle | Date | Mon, 17 Oct 2022 17:53:42 +0800 |
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KASAN reported a null-ptr-deref error:
KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f] CPU: 0 PID: 1373 Comm: modprobe Hardware name: QEMU Standard PC (i440FX + PIIX, 1996) RIP: 0010:dmi_sysfs_entry_release ... Call Trace: <TASK> kobject_put dmi_sysfs_register_handle (drivers/firmware/dmi-sysfs.c:540) dmi_sysfs dmi_decode_table (drivers/firmware/dmi_scan.c:133) dmi_walk (drivers/firmware/dmi_scan.c:1115) dmi_sysfs_init (drivers/firmware/dmi-sysfs.c:149) dmi_sysfs do_one_initcall (init/main.c:1296) ... Kernel panic - not syncing: Fatal exception Kernel Offset: 0x4000000 from 0xffffffff81000000 ---[ end Kernel panic - not syncing: Fatal exception ]---
It is because previous patch added kobject_put() to release the memory which will call dmi_sysfs_entry_release() and list_del().
However, list_add_tail(entry->list) is called after the error block, so the list_head is uninitialized and cannot be deleted.
Because entry is allocated by kzalloc() so the list.prev is NULL in the error path. Check it in dmi_sysfs_entry_release() to avoid deleting uninitialized list_head.
Fixes: 660ba678f999 ("firmware: dmi-sysfs: Fix memory leak in dmi_sysfs_register_handle")
Signed-off-by: Chen Zhongjin <chenzhongjin@huawei.com> --- drivers/firmware/dmi-sysfs.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/drivers/firmware/dmi-sysfs.c b/drivers/firmware/dmi-sysfs.c index 66727ad3361b..f8815eeed00c 100644 --- a/drivers/firmware/dmi-sysfs.c +++ b/drivers/firmware/dmi-sysfs.c @@ -557,9 +557,12 @@ static void dmi_sysfs_entry_release(struct kobject *kobj) { struct dmi_sysfs_entry *entry = to_entry(kobj); - spin_lock(&entry_list_lock); - list_del(&entry->list); - spin_unlock(&entry_list_lock); + if (entry->list.prev != NULL) { + spin_lock(&entry_list_lock); + list_del(&entry->list); + spin_unlock(&entry_list_lock); + } + kfree(entry); } -- 2.17.1
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