github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-05-12 16:18:45 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity

lib/bch: fix signed left-shift undefined behavior

Browse Source 
Patch series "lib/bch: fix undefined behavior from signed left-shifts".

Fix two instances of undefined behavior in lib/bch.c caused by
left-shifting signed integers into or past the sign bit.

While the kernel's -fno-strict-overflow flag prevents miscompilation
today, these are formally UB per C11 6.5.7p4 and trivial to fix.


This patch (of 2):

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.

Link: https://lkml.kernel.org/r/20260318074806.16527-2-objecting@objecting.org
Signed-off-by: Josh Law <objecting@objecting.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Ivan Djelic <ivan.djelic@parrot.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Josh Law 2026-03-18 07:48:05 +00:00 committed by Andrew Morton
parent b8822d73d6
commit f42b510990
1 changed files with 2 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
lib/bch.c
View File

@ -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) {