From 8a7ef96e6af91f0fdd3aa9ec25a45ec2431f718d Mon Sep 17 00:00:00 2001 From: Veerendranath Jakkam Date: Fri, 9 Jan 2026 20:30:04 +0530 Subject: [PATCH] wifi: cfg80211: Fix bitrate calculation overflow for HE rates [ Upstream commit a3034bf0746d88a00cceda9541534a5721445a24 ] An integer overflow occurs in cfg80211_calculate_bitrate_he() when calculating bitrates for high throughput HE configurations. For example, with 160 MHz bandwidth, HE-MCS 13, HE-NSS 4, and HE-GI 0, the multiplication (result * rate->nss) overflows the 32-bit 'result' variable before division by 8, leading to significantly underestimated bitrate values. The overflow occurs because the NSS multiplication operates on a 32-bit integer that cannot accommodate intermediate values exceeding 4,294,967,295. When overflow happens, the value wraps around, producing incorrect bitrates for high MCS and NSS combinations. Fix this by utilizing the 64-bit 'tmp' variable for the NSS multiplication and subsequent divisions via do_div(). This approach preserves full precision throughout the entire calculation, with the final value assigned to 'result' only after completing all operations. Signed-off-by: Veerendranath Jakkam Link: https://patch.msgid.link/20260109-he_bitrate_overflow-v1-1-95575e466b6e@oss.qualcomm.com Signed-off-by: Johannes Berg Signed-off-by: Sasha Levin --- net/wireless/util.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/net/wireless/util.c b/net/wireless/util.c index 4eb028ad1683..81d6d27d273c 100644 --- a/net/wireless/util.c +++ b/net/wireless/util.c @@ -1561,12 +1561,14 @@ static u32 cfg80211_calculate_bitrate_he(struct rate_info *rate) tmp = result; tmp *= SCALE; do_div(tmp, mcs_divisors[rate->mcs]); - result = tmp; /* and take NSS, DCM into account */ - result = (result * rate->nss) / 8; + tmp *= rate->nss; + do_div(tmp, 8); if (rate->he_dcm) - result /= 2; + do_div(tmp, 2); + + result = tmp; return result / 10000; }