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a=openpgp; fpr=E8CB85F76877057A6E27F77AF6B7824F4269A073 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Nathan reported this issue: $ make -skj"$(nproc)" ARCH=3Dx86_64 LLVM=3D1 LLVM_IAS=3D1 mrproper allmod= config 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 =3D !!(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 alwa= ys false 877 | if (WARN_ON_ONCE(offset > skb->len)) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 878 | goto out; | ~~~~~~~~ net/mptcp/subflow.c:874:18: note: initialize the variable 'incr' to silen= ce this warning 874 | u32 offset, incr, avail_len; | ^ | =3D 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 Closes: https://lore.kernel.org/20240928175524.GA1713144@thelio-3990X Signed-off-by: Matthieu Baerts (NGI0) --- net/mptcp/subflow.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index 8a0ef50c307c..843c61ebd421 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -871,7 +871,7 @@ static void mptcp_subflow_discard_data(struct sock *ssk= , struct sk_buff *skb, struct mptcp_subflow_context *subflow =3D mptcp_subflow_ctx(ssk); bool fin =3D TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN; struct tcp_sock *tp =3D tcp_sk(ssk); - u32 offset, incr, avail_len; + u32 offset, incr =3D 0, avail_len; =20 offset =3D tp->copied_seq - TCP_SKB_CB(skb)->seq; if (WARN_ON_ONCE(offset > skb->len)) --=20 2.45.2