* [PATCH AUTOSEL 5.10 6/7] sctp: Fix undefined behavior in left shift operation
[not found] <20250224112051.2215017-1-sashal@kernel.org>
@ 2025-02-24 11:20 ` Sasha Levin
0 siblings, 0 replies; only message in thread
From: Sasha Levin @ 2025-02-24 11:20 UTC (permalink / raw)
To: linux-kernel, stable
Cc: Yu-Chun Lin, Jakub Kicinski, Sasha Levin, marcelo.leitner,
lucien.xin, davem, edumazet, pabeni, linux-sctp, netdev
From: Yu-Chun Lin <eleanor15x@gmail.com>
[ Upstream commit 606572eb22c1786a3957d24307f5760bb058ca19 ]
According to the C11 standard (ISO/IEC 9899:2011, 6.5.7):
"If E1 has a signed type and E1 x 2^E2 is not representable in the result
type, the behavior is undefined."
Shifting 1 << 31 causes signed integer overflow, which leads to undefined
behavior.
Fix this by explicitly using '1U << 31' to ensure the shift operates on
an unsigned type, avoiding undefined behavior.
Signed-off-by: Yu-Chun Lin <eleanor15x@gmail.com>
Link: https://patch.msgid.link/20250218081217.3468369-1-eleanor15x@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/sctp/stream.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/sctp/stream.c b/net/sctp/stream.c
index ee6514af830f7..0527728aee986 100644
--- a/net/sctp/stream.c
+++ b/net/sctp/stream.c
@@ -735,7 +735,7 @@ struct sctp_chunk *sctp_process_strreset_tsnreq(
* value SHOULD be the smallest TSN not acknowledged by the
* receiver of the request plus 2^31.
*/
- init_tsn = sctp_tsnmap_get_ctsn(&asoc->peer.tsn_map) + (1 << 31);
+ init_tsn = sctp_tsnmap_get_ctsn(&asoc->peer.tsn_map) + (1U << 31);
sctp_tsnmap_init(&asoc->peer.tsn_map, SCTP_TSN_MAP_INITIAL,
init_tsn, GFP_ATOMIC);
--
2.39.5
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