From: Lukas Wunner <lukas@wunner.de> mainline inclusion from mainline-v6.15-rc1 commit b16510a530d1e6ab9683f04f8fb34f2e0f538275 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IC9953 CVE: CVE-2025-37984 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... ---------------------------------------------------------------------- Herbert notes that DIV_ROUND_UP() may overflow unnecessarily if an ecdsa implementation's ->key_size() callback returns an unusually large value. Herbert instead suggests (for a division by 8): X / 8 + !!(X & 7) Based on this formula, introduce a generic DIV_ROUND_UP_POW2() macro and use it in lieu of DIV_ROUND_UP() for ->key_size() return values. Additionally, use the macro in ecc_digits_from_bytes(), whose "nbytes" parameter is a ->key_size() return value in some instances, or a user-specified ASN.1 length in the case of ecdsa_get_signature_rs(). Link: https://lore.kernel.org/r/Z3iElsILmoSu6FuC@gondor.apana.org.au/ Signed-off-by: Lukas Wunner <lukas@wunner.de> Signed-off-by: Lukas Wunner <lukas@wunner.de> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Conflicts: crypto/ecdsa-p1363.c crypto/ecdsa-x962.c [p1363 and x932 are not merged] Signed-off-by: Chen Ridong <chenridong@huawei.com> --- crypto/ecc.c | 2 +- include/linux/math.h | 12 ++++++++++++ 2 files changed, 13 insertions(+), 1 deletion(-) diff --git a/crypto/ecc.c b/crypto/ecc.c index 21504280aca2e..27fcecf3a61fb 100644 --- a/crypto/ecc.c +++ b/crypto/ecc.c @@ -69,7 +69,7 @@ EXPORT_SYMBOL(ecc_get_curve); void ecc_digits_from_bytes(const u8 *in, unsigned int nbytes, u64 *out, unsigned int ndigits) { - int diff = ndigits - DIV_ROUND_UP(nbytes, sizeof(u64)); + int diff = ndigits - DIV_ROUND_UP_POW2(nbytes, sizeof(u64)); unsigned int o = nbytes & 7; __be64 msd = 0; diff --git a/include/linux/math.h b/include/linux/math.h index dd4152711de7d..ee754ec3dc929 100644 --- a/include/linux/math.h +++ b/include/linux/math.h @@ -34,6 +34,18 @@ */ #define round_down(x, y) ((x) & ~__round_mask(x, y)) +/** + * DIV_ROUND_UP_POW2 - divide and round up + * @n: numerator + * @d: denominator (must be a power of 2) + * + * Divides @n by @d and rounds up to next multiple of @d (which must be a power + * of 2). Avoids integer overflows that may occur with __KERNEL_DIV_ROUND_UP(). + * Performance is roughly equivalent to __KERNEL_DIV_ROUND_UP(). + */ +#define DIV_ROUND_UP_POW2(n, d) \ + ((n) / (d) + !!((n) & ((d) - 1))) + #define DIV_ROUND_UP __KERNEL_DIV_ROUND_UP #define DIV_ROUND_DOWN_ULL(ll, d) \ -- 2.34.1