Re: [PATCH bpf 1/2] bpf, sockmap: Don't leak UDP socks on lookup-bind-release
From: John Fastabend <john.fastabend@gmail.com>
Date: 2026-06-26 21:43:12
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bpf, linux-kselftest, lkml
On Thu, Jun 25, 2026 at 12:48:55PM +0200, Jakub Sitnicki wrote:
On Wed, Jun 24, 2026 at 02:39 PM -07, Kuniyuki Iwashima wrote:quoted
On Wed, Jun 24, 2026 at 2:33 PM Kuniyuki Iwashima [off-list ref] wrote:quoted
On Wed, Jun 24, 2026 at 2:26 PM Michal Luczaj [off-list ref] wrote:quoted
On 6/24/26 22:01, Willem de Bruijn wrote:quoted
Jakub Sitnicki wrote:quoted
On Tue, Jun 23, 2026 at 08:03 PM +02, Michal Luczaj wrote:quoted
UDP sockets get SOCK_RCU_FREE set when (auto-)bound. This means sk_is_refcounted(unbound) = true, while sk_is_refcounted(bound) = false. Because sockmap accepts unbound UDP sockets, a BPF program can increment a socket's refcount via lookup. If the socket is subsequently bound, the transition from unbound to bound causes bpf_sk_release() to skip the decrement of the refcount, causing a memory leak. unreferenced object 0xffff88810bc2eb40 (size 1984): comm "test_progs", pid 2451, jiffies 4295320596 hex dump (first 32 bytes): 7f 00 00 01 7f 00 00 01 d2 04 1b b7 04 d2 00 00 ................ 02 00 01 40 00 00 00 00 00 00 00 00 00 00 00 00 ...@............ backtrace (crc bdee079d): kmem_cache_alloc_noprof+0x557/0x660 sk_prot_alloc+0x69/0x240 sk_alloc+0x30/0x460 inet_create+0x2ce/0xf80 __sock_create+0x25b/0x5c0 __sys_socket+0x119/0x1d0 __x64_sys_socket+0x72/0xd0 do_syscall_64+0xa1/0x5f0 entry_SYSCALL_64_after_hwframe+0x76/0x7e Maintain balanced refcounts across sk lookup/release: (re-)set SOCK_RCU_FREE on proto update to treat the socket (whether bound or unbound) as not requiring a refcount increment on (a RCU protected) lookup. Fixes: 0c48eefae712 ("sock_map: Lift socket state restriction for datagram sockets") Signed-off-by: Michal Luczaj <redacted>
[...]
Rejecting unhashed UDP sockets on insert to sockmap SGTM. It is also in line with disable-problematic-cases strategy.
Agree ACK just disallow it.