Commit 606572eb authored by Yu-Chun Lin's avatar Yu-Chun Lin Committed by Jakub Kicinski
Browse files

sctp: Fix undefined behavior in left shift operation 



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: default avatarYu-Chun Lin <eleanor15x@gmail.com>
Link: https://patch.msgid.link/20250218081217.3468369-1-eleanor15x@gmail.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 5bcd3d15

net/sctp/stream.c

+1 −1
Original line number Diff line number Diff line
@@ -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);