6.6-stable review patch. If anyone has any objections, please let me know.
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From: Jiayuan Chen jiayuan.chen@linux.dev
[ Upstream commit 54a3ecaeeeae8176da8badbd7d72af1017032c39 ]
[ 2172.936997] ------------[ cut here ]------------ [ 2172.936999] kernel BUG at lib/iov_iter.c:629! ...... [ 2172.944996] PKRU: 55555554 [ 2172.945155] Call Trace: [ 2172.945299] <TASK> [ 2172.945428] ? die+0x36/0x90 [ 2172.945601] ? do_trap+0xdd/0x100 [ 2172.945795] ? iov_iter_revert+0x178/0x180 [ 2172.946031] ? iov_iter_revert+0x178/0x180 [ 2172.946267] ? do_error_trap+0x7d/0x110 [ 2172.946499] ? iov_iter_revert+0x178/0x180 [ 2172.946736] ? exc_invalid_op+0x50/0x70 [ 2172.946961] ? iov_iter_revert+0x178/0x180 [ 2172.947197] ? asm_exc_invalid_op+0x1a/0x20 [ 2172.947446] ? iov_iter_revert+0x178/0x180 [ 2172.947683] ? iov_iter_revert+0x5c/0x180 [ 2172.947913] tls_sw_sendmsg_locked.isra.0+0x794/0x840 [ 2172.948206] tls_sw_sendmsg+0x52/0x80 [ 2172.948420] ? inet_sendmsg+0x1f/0x70 [ 2172.948634] __sys_sendto+0x1cd/0x200 [ 2172.948848] ? find_held_lock+0x2b/0x80 [ 2172.949072] ? syscall_trace_enter+0x140/0x270 [ 2172.949330] ? __lock_release.isra.0+0x5e/0x170 [ 2172.949595] ? find_held_lock+0x2b/0x80 [ 2172.949817] ? syscall_trace_enter+0x140/0x270 [ 2172.950211] ? lockdep_hardirqs_on_prepare+0xda/0x190 [ 2172.950632] ? ktime_get_coarse_real_ts64+0xc2/0xd0 [ 2172.951036] __x64_sys_sendto+0x24/0x30 [ 2172.951382] do_syscall_64+0x90/0x170 ......
After calling bpf_exec_tx_verdict(), the size of msg_pl->sg may increase, e.g., when the BPF program executes bpf_msg_push_data().
If the BPF program sets cork_bytes and sg.size is smaller than cork_bytes, it will return -ENOSPC and attempt to roll back to the non-zero copy logic. However, during rollback, msg->msg_iter is reset, but since msg_pl->sg.size has been increased, subsequent executions will exceed the actual size of msg_iter. ''' iov_iter_revert(&msg->msg_iter, msg_pl->sg.size - orig_size); '''
The changes in this commit are based on the following considerations:
1. When cork_bytes is set, rolling back to non-zero copy logic is pointless and can directly go to zero-copy logic.
2. We can not calculate the correct number of bytes to revert msg_iter.
Assume the original data is "abcdefgh" (8 bytes), and after 3 pushes by the BPF program, it becomes 11-byte data: "abc?de?fgh?". Then, we set cork_bytes to 6, which means the first 6 bytes have been processed, and the remaining 5 bytes "?fgh?" will be cached until the length meets the cork_bytes requirement.
However, some data in "?fgh?" is not within 'sg->msg_iter' (but in msg_pl instead), especially the data "?" we pushed.
So it doesn't seem as simple as just reverting through an offset of msg_iter.
3. For non-TLS sockets in tcp_bpf_sendmsg, when a "cork" situation occurs, the user-space send() doesn't return an error, and the returned length is the same as the input length parameter, even if some data is cached.
Additionally, I saw that the current non-zero-copy logic for handling corking is written as: ''' line 1177 else if (ret != -EAGAIN) { if (ret == -ENOSPC) ret = 0; goto send_end; '''
So it's ok to just return 'copied' without error when a "cork" situation occurs.
Fixes: fcb14cb1bdac ("new iov_iter flavour - ITER_UBUF") Fixes: d3b18ad31f93 ("tls: add bpf support to sk_msg handling") Signed-off-by: Jiayuan Chen jiayuan.chen@linux.dev Acked-by: John Fastabend john.fastabend@gmail.com Link: https://lore.kernel.org/r/20250219052015.274405-2-jiayuan.chen@linux.dev Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/tls/tls_sw.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c index 6e30fe879d538..bf445a518883a 100644 --- a/net/tls/tls_sw.c +++ b/net/tls/tls_sw.c @@ -1120,9 +1120,13 @@ static int tls_sw_sendmsg_locked(struct sock *sk, struct msghdr *msg, num_async++; else if (ret == -ENOMEM) goto wait_for_memory; - else if (ctx->open_rec && ret == -ENOSPC) + else if (ctx->open_rec && ret == -ENOSPC) { + if (msg_pl->cork_bytes) { + ret = 0; + goto send_end; + } goto rollback_iter; - else if (ret != -EAGAIN) + } else if (ret != -EAGAIN) goto send_end; } continue;