5.10-stable review patch. If anyone has any objections, please let me know.
------------------
From: "Matthieu Baerts (NGI0)" matttbe@kernel.org
Nathan reported this issue:
$ make -skj"$(nproc)" ARCH=x86_64 LLVM=1 LLVM_IAS=1 mrproper allmodconfig net/mptcp/subflow.o net/mptcp/subflow.c:877:6: warning: variable 'incr' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized] 877 | if (WARN_ON_ONCE(offset > skb->len)) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ include/asm-generic/bug.h:101:33: note: expanded from macro 'WARN_ON_ONCE' 101 | #define WARN_ON_ONCE(condition) ({ \ | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 102 | int __ret_warn_on = !!(condition); \ | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 103 | if (unlikely(__ret_warn_on)) \ | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 104 | __WARN_FLAGS(BUGFLAG_ONCE | \ | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 105 | BUGFLAG_TAINT(TAINT_WARN)); \ | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 106 | unlikely(__ret_warn_on); \ | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 107 | }) | ~~ net/mptcp/subflow.c:893:6: note: uninitialized use occurs here 893 | if (incr) | ^~~~ net/mptcp/subflow.c:877:2: note: remove the 'if' if its condition is always false 877 | if (WARN_ON_ONCE(offset > skb->len)) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 878 | goto out; | ~~~~~~~~ net/mptcp/subflow.c:874:18: note: initialize the variable 'incr' to silence this warning 874 | u32 offset, incr, avail_len; | ^ | = 0 1 warning generated.
As mentioned by Nathan, this issue is present because 5.10 does not include commit ea4ca586b16f ("mptcp: refine MPTCP-level ack scheduling"), which removed the use of 'incr' in the error path added by this change. This other commit does not really look suitable for stable, hence this dedicated patch for 5.10.
Fixes: e93fa44f0714 ("mptcp: fix duplicate data handling") Reported-by: Nathan Chancellor nathan@kernel.org Closes: https://lore.kernel.org/20240928175524.GA1713144@thelio-3990X Signed-off-by: Matthieu Baerts (NGI0) matttbe@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/mptcp/subflow.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -871,7 +871,7 @@ static void mptcp_subflow_discard_data(s struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk); bool fin = TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN; struct tcp_sock *tp = tcp_sk(ssk); - u32 offset, incr, avail_len; + u32 offset, incr = 0, avail_len;
offset = tp->copied_seq - TCP_SKB_CB(skb)->seq; if (WARN_ON_ONCE(offset > skb->len))