UBUNTU-CVE-2026-98737: Use After Free

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: hcisync: Fix inquiry cache use-after-free The sync command worker holds hdev->reqlock, but inquiry-cache updates and flushes use hdev->lock. Both hciaclcreateconnsync() and hcistopdiscoverysync() look up entries and read their fields without taking hdev->lock. After either lookup returns, a concurrent HCIINQUIRY ioctl can acquire hdev->lock and flush the cache, freeing the entry. The worker then reads the freed entry while preparing a create-connection or remote-name-cancel command. The list traversal also races with cache updates and removal. KASAN reported these accesses: BUG: KASAN: slab-use-after-free in hciaclcreateconnsync+0x5f1/0x650 Workqueue: hci0 hcicmdsyncwork Call Trace: hciaclcreateconnsync+0x5f1/0x650 hcicmdsyncwork+0x13c/0x290 Allocated by task 90: hciinquirycacheupdate+0x3e6/0x7d0 hciinquiryresultevt+0x3cb/0x560 Freed by task 93: hciinquirycacheflush+0x111/0x2b0 hciinquiry+0x2f2/0x780 hcisockioctl+0x269/0x5f0 BUG: KASAN: slab-use-after-free in hcistopdiscoverysync+0x3b1/0x3c0 Workqueue: hci0 hcicmdsyncwork Call Trace: hcistopdiscoverysync+0x3b1/0x3c0 hcicmdsyncwork+0x173/0x300 Allocated by task 86: hciinquirycacheupdate+0x483/0x940 hciinquiryresultevt+0x3cb/0x560 Freed by task 91: hciinquirycacheflush+0x13e/0x2f0 hciinquiry+0x2f2/0x780 hcisockioctl+0x269/0x5f0 Hold hdev->lock across each lookup and all reads from its result. Copy the remote address before unlocking so discovery cancellation does not retain a cache entry pointer. Release the lock before sending synchronous HCI commands, since their completion handlers may need the same lock.