From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BF438423A7C; Tue, 31 Mar 2026 16:48:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774975722; cv=none; b=uUQAoTf8Yc2PhLviOcqav+w+xg9xJ72npwIxsj3Zy3j1WEagGdbeJW6x6UedpmiLLz4JQOACcD89yvLFzGcIWeQz0GcNhzaWME+TCjEZaWK4kyUAo17c8YJXYPWI1JLIecmKAeiuFzO/ut/8GC/b0vBQzRtQQMPInvv+TS0kJ4A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774975722; c=relaxed/simple; bh=ZB4BJD9jLLB+Z9//yjP7VJT9EV7auOAQwqozGrQaSvY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=CD6CYdo61duVcjFGRGUdDCuY9dNG/SiyTyw7fH1We+xFxzZeb3N4YknH8BDdzoerbALw2diCUSwBnyT2viacamDh2t4iykw1g1vh1Qx0ctEejqoCwzULogXJZSCSGSvS/mKHfZvdrJ59YULRPZrQR1EC8+hlMosq88lBf0ZvRX8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=zAyi2NvW; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="zAyi2NvW" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 56A8CC19423; Tue, 31 Mar 2026 16:48:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1774975722; bh=ZB4BJD9jLLB+Z9//yjP7VJT9EV7auOAQwqozGrQaSvY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=zAyi2NvWhNn5RwMQQYbONUPgHsGyNXjiV24UK2h8qrpmmgQaFIyfRSjVUM9HyaWmb rmvH1C/p8n089yO7SX/c/HjiwUrQ9/5nTPs4+CIz5czfcX0rdVc8Zd2T45QV9+gFqT AOb8KXLkWNgF0UUG1pIBQuDB5dBtJf+GQrP7zz1U= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Andrea Righi , Emil Tsalapatis , Shung-Hsi Yu , Eduard Zingerman , Alexei Starovoitov , Sasha Levin Subject: [PATCH 6.12 034/244] bpf: Fix u32/s32 bounds when ranges cross min/max boundary Date: Tue, 31 Mar 2026 18:19:44 +0200 Message-ID: <20260331161742.960922011@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260331161741.651718120@linuxfoundation.org> References: <20260331161741.651718120@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eduard Zingerman [ Upstream commit fbc7aef517d8765e4c425d2792409bb9bf2e1f13 ] Same as in __reg64_deduce_bounds(), refine s32/u32 ranges in __reg32_deduce_bounds() in the following situations: - s32 range crosses U32_MAX/0 boundary, positive part of the s32 range overlaps with u32 range: 0 U32_MAX | [xxxxxxxxxxxxxx u32 range xxxxxxxxxxxxxx] | |----------------------------|----------------------------| |xxxxx s32 range xxxxxxxxx] [xxxxxxx| 0 S32_MAX S32_MIN -1 - s32 range crosses U32_MAX/0 boundary, negative part of the s32 range overlaps with u32 range: 0 U32_MAX | [xxxxxxxxxxxxxx u32 range xxxxxxxxxxxxxx] | |----------------------------|----------------------------| |xxxxxxxxx] [xxxxxxxxxxxx s32 range | 0 S32_MAX S32_MIN -1 - No refinement if ranges overlap in two intervals. This helps for e.g. consider the following program: call %[bpf_get_prandom_u32]; w0 &= 0xffffffff; if w0 < 0x3 goto 1f; // on fall-through u32 range [3..U32_MAX] if w0 s> 0x1 goto 1f; // on fall-through s32 range [S32_MIN..1] if w0 s< 0x0 goto 1f; // range can be narrowed to [S32_MIN..-1] r10 = 0; 1: ...; The reg_bounds.c selftest is updated to incorporate identical logic, refinement based on non-overflowing range halves: ((x ∩ [0, smax]) ∩ (y ∩ [0, smax])) ∪ ((x ∩ [smin,-1]) ∩ (y ∩ [smin,-1])) Reported-by: Andrea Righi Reported-by: Emil Tsalapatis Closes: https://lore.kernel.org/bpf/aakqucg4vcujVwif@gpd4/T/ Reviewed-by: Emil Tsalapatis Acked-by: Shung-Hsi Yu Signed-off-by: Eduard Zingerman Link: https://lore.kernel.org/r/20260306-bpf-32-bit-range-overflow-v3-1-f7f67e060a6b@gmail.com Signed-off-by: Alexei Starovoitov Signed-off-by: Sasha Levin --- kernel/bpf/verifier.c | 24 +++++++ .../selftests/bpf/prog_tests/reg_bounds.c | 62 +++++++++++++++++-- 2 files changed, 82 insertions(+), 4 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 68fa30852051e..0195726266f4d 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -2046,6 +2046,30 @@ static void __reg32_deduce_bounds(struct bpf_reg_state *reg) if ((u32)reg->s32_min_value <= (u32)reg->s32_max_value) { reg->u32_min_value = max_t(u32, reg->s32_min_value, reg->u32_min_value); reg->u32_max_value = min_t(u32, reg->s32_max_value, reg->u32_max_value); + } else { + if (reg->u32_max_value < (u32)reg->s32_min_value) { + /* See __reg64_deduce_bounds() for detailed explanation. + * Refine ranges in the following situation: + * + * 0 U32_MAX + * | [xxxxxxxxxxxxxx u32 range xxxxxxxxxxxxxx] | + * |----------------------------|----------------------------| + * |xxxxx s32 range xxxxxxxxx] [xxxxxxx| + * 0 S32_MAX S32_MIN -1 + */ + reg->s32_min_value = (s32)reg->u32_min_value; + reg->u32_max_value = min_t(u32, reg->u32_max_value, reg->s32_max_value); + } else if ((u32)reg->s32_max_value < reg->u32_min_value) { + /* + * 0 U32_MAX + * | [xxxxxxxxxxxxxx u32 range xxxxxxxxxxxxxx] | + * |----------------------------|----------------------------| + * |xxxxxxxxx] [xxxxxxxxxxxx s32 range | + * 0 S32_MAX S32_MIN -1 + */ + reg->s32_max_value = (s32)reg->u32_max_value; + reg->u32_min_value = max_t(u32, reg->u32_min_value, reg->s32_min_value); + } } } diff --git a/tools/testing/selftests/bpf/prog_tests/reg_bounds.c b/tools/testing/selftests/bpf/prog_tests/reg_bounds.c index 39d42271cc460..ac4e2557f7391 100644 --- a/tools/testing/selftests/bpf/prog_tests/reg_bounds.c +++ b/tools/testing/selftests/bpf/prog_tests/reg_bounds.c @@ -422,15 +422,69 @@ static bool is_valid_range(enum num_t t, struct range x) } } -static struct range range_improve(enum num_t t, struct range old, struct range new) +static struct range range_intersection(enum num_t t, struct range old, struct range new) { return range(t, max_t(t, old.a, new.a), min_t(t, old.b, new.b)); } +/* + * Result is precise when 'x' and 'y' overlap or form a continuous range, + * result is an over-approximation if 'x' and 'y' do not overlap. + */ +static struct range range_union(enum num_t t, struct range x, struct range y) +{ + if (!is_valid_range(t, x)) + return y; + if (!is_valid_range(t, y)) + return x; + return range(t, min_t(t, x.a, y.a), max_t(t, x.b, y.b)); +} + +/* + * This function attempts to improve x range intersecting it with y. + * range_cast(... to_t ...) looses precision for ranges that pass to_t + * min/max boundaries. To avoid such precision loses this function + * splits both x and y into halves corresponding to non-overflowing + * sub-ranges: [0, smin] and [smax, -1]. + * Final result is computed as follows: + * + * ((x ∩ [0, smax]) ∩ (y ∩ [0, smax])) ∪ + * ((x ∩ [smin,-1]) ∩ (y ∩ [smin,-1])) + * + * Precision might still be lost if final union is not a continuous range. + */ +static struct range range_refine_in_halves(enum num_t x_t, struct range x, + enum num_t y_t, struct range y) +{ + struct range x_pos, x_neg, y_pos, y_neg, r_pos, r_neg; + u64 smax, smin, neg_one; + + if (t_is_32(x_t)) { + smax = (u64)(u32)S32_MAX; + smin = (u64)(u32)S32_MIN; + neg_one = (u64)(u32)(s32)(-1); + } else { + smax = (u64)S64_MAX; + smin = (u64)S64_MIN; + neg_one = U64_MAX; + } + x_pos = range_intersection(x_t, x, range(x_t, 0, smax)); + x_neg = range_intersection(x_t, x, range(x_t, smin, neg_one)); + y_pos = range_intersection(y_t, y, range(x_t, 0, smax)); + y_neg = range_intersection(y_t, y, range(y_t, smin, neg_one)); + r_pos = range_intersection(x_t, x_pos, range_cast(y_t, x_t, y_pos)); + r_neg = range_intersection(x_t, x_neg, range_cast(y_t, x_t, y_neg)); + return range_union(x_t, r_pos, r_neg); + +} + static struct range range_refine(enum num_t x_t, struct range x, enum num_t y_t, struct range y) { struct range y_cast; + if (t_is_32(x_t) == t_is_32(y_t)) + x = range_refine_in_halves(x_t, x, y_t, y); + y_cast = range_cast(y_t, x_t, y); /* If we know that @@ -444,7 +498,7 @@ static struct range range_refine(enum num_t x_t, struct range x, enum num_t y_t, */ if (x_t == S64 && y_t == S32 && y_cast.a <= S32_MAX && y_cast.b <= S32_MAX && (s64)x.a >= S32_MIN && (s64)x.b <= S32_MAX) - return range_improve(x_t, x, y_cast); + return range_intersection(x_t, x, y_cast); /* the case when new range knowledge, *y*, is a 32-bit subregister * range, while previous range knowledge, *x*, is a full register @@ -462,11 +516,11 @@ static struct range range_refine(enum num_t x_t, struct range x, enum num_t y_t, x_swap = range(x_t, swap_low32(x.a, y_cast.a), swap_low32(x.b, y_cast.b)); if (!is_valid_range(x_t, x_swap)) return x; - return range_improve(x_t, x, x_swap); + return range_intersection(x_t, x, x_swap); } /* otherwise, plain range cast and intersection works */ - return range_improve(x_t, x, y_cast); + return range_intersection(x_t, x, y_cast); } /* ======================= -- 2.51.0