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sctp: Fix undefined behavior in left shift operation

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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>
This commit is contained in:
Yu-Chun Lin 2025-02-18 16:12:16 +08:00 • committed by Jakub Kicinski
parent 5bcd3d15ca
commit 606572eb22
1 changed files with 1 additions and 1 deletions
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2
net/sctp/stream.c
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@ -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);