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

Josh Law posted 2 patches 2 weeks, 5 days ago
[PATCH 1/2] lib/bch: fix signed left-shift undefined behavior
Posted by Josh Law 2 weeks, 5 days ago
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@objecting.org>
---
 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