[PATCH 1/2] lib/bch: fix signed left-shift undefined behavior

From: Josh Law

Date: Wed Mar 18 2026 - 03:48:56 EST


Use 1u instead of 1 to avoid undefined behavior when left-shifting
into the sign bit of a signed int. deg() can return up to 31, and
1 << 31 is UB per C11.

Signed-off-by: Josh Law <objecting@xxxxxxxxxxxxx>
---
lib/bch.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/bch.c b/lib/bch.c
index 9561c0828802..ef733f08082f 100644
--- a/lib/bch.c
+++ b/lib/bch.c
@@ -392,7 +392,7 @@ static void compute_syndromes(struct bch_control *bch, uint32_t *ecc,
for (j = 0; j < 2*t; j += 2)
syn[j] ^= a_pow(bch, (j+1)*(i+s));

- poly ^= (1 << i);
+ poly ^= (1u << i);
}
} while (s > 0);

@@ -612,7 +612,7 @@ static int find_poly_deg2_roots(struct bch_control *bch, struct gf_poly *poly,
while (v) {
i = deg(v);
r ^= bch->xi_tab[i];
- v ^= (1 << i);
+ v ^= (1u << i);
}
/* verify root */
if ((gf_sqr(bch, r)^r) == u) {
--
2.34.1