Affected: Linux

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

ax25: Remove broken autobind

Binding AX25 socket by using the autobind feature leads to memory leaks in ax25_connect() and also refcount leaks in ax25_release(). Memory leak was detected with kmemleak:

================================================================ unreferenced object 0xffff8880253cd680 (size 96): backtrace: __kmalloc_node_track_caller_noprof (./include/linux/kmemleak.h:43) kmemdup_noprof (mm/util.c:136) ax25_rt_autobind (net/ax25/ax25_route.c:428) ax25_connect (net/ax25/af_ax25.c:1282) __sys_connect_file (net/socket.c:2045) __sys_connect (net/socket.c:2064) __x64_sys_connect (net/socket.c:2067) do_syscall_64 (arch/x86/entry/common.c:52 arch/x86/entry/common.c:83) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) ================================================================

When socket is bound, refcounts must be incremented the way it is done in ax25_bind() and ax25_setsockopt() (SO_BINDTODEVICE). In case of autobind, the refcounts are not incremented.

This bug leads to the following issue reported by Syzkaller:

================================================================ ax25_connect(): syz-executor318 uses autobind, please contact jreuter@yaina.de ------------[ cut here ]------------ refcount_t: decrement hit 0; leaking memory. WARNING: CPU: 0 PID: 5317 at lib/refcount.c:31 refcount_warn_saturate+0xfa/0x1d0 lib/refcount.c:31 Modules linked in: CPU: 0 UID: 0 PID:…