CVE-2024-36013

In the Linux kernel, the following vulnerability has been resolved:

Bluetooth: L2CAP: Fix slab-use-after-free in l2cap_connect()

Extend a critical section to prevent chan from early freeing. Also make the l2cap_connect() return type void. Nothing is using the returned value but it is ugly to return a potentially freed pointer. Making it void will help with backports because earlier kernels did use the return value. Now the compile will break for kernels where this patch is not a complete fix.

Call stack summary:

[use] l2cap_bredr_sig_cmd l2cap_connect ┌ mutex_lock(&conn->chan_lock); │ chan = pchan->ops->new_connection(pchan); <- alloc chan │ __l2cap_chan_add(conn, chan); │ l2cap_chan_hold(chan); │ list_add(&chan->list, &conn->chan_l); … (1) └ mutex_unlock(&conn->chan_lock); chan->conf_state … (4) <- use after free

[free] l2cap_conn_del ┌ mutex_lock(&conn->chan_lock); │ foreach chan in conn->chan_l: … (2) │ l2cap_chan_put(chan); │ l2cap_chan_destroy │ kfree(chan) … (3) <- chan freed └ mutex_unlock(&conn->chan_lock);

================================================================== BUG: KASAN: slab-use-after-free in instrument_atomic_read include/linux/instrumented.h:68 [inline] BUG: KASAN: slab-use-after-free in _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline] BUG: KASAN: slab-use-after-free in l2cap_connect+0xa67/0x11a0 net/bluetooth/l2cap_core.c:4260 Read of size 8 at addr ffff88810bf040a0 by task kworker/u3:1/311

Weakness

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/4d7b41c0e43995b0e992b9f8903109275744b658
• https://git.kernel.org/stable/c/826af9d2f69567c646ff46d10393d47e30ad23c6
• https://git.kernel.org/stable/c/cfe560c7050bfb37b0d2491bbe7cd8b59e77fdc5
• http://www.openwall.com/lists/oss-security/2024/05/30/1
• http://www.openwall.com/lists/oss-security/2024/05/30/2
• https://git.kernel.org/stable/c/4d7b41c0e43995b0e992b9f8903109275744b658
• https://git.kernel.org/stable/c/826af9d2f69567c646ff46d10393d47e30ad23c6
• https://git.kernel.org/stable/c/cfe560c7050bfb37b0d2491bbe7cd8b59e77fdc5