From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794590541; b=jqIxjCN+Nb/fX+5SwO4w80rbtDEpTU6gF9S1qS6KP9EHmL7oIswMApBJhiq9GcGEoMNh 9549vk99y4ac5C1MevcfcdE7Hmd4loRVCKk1QDEP5cRuUpf68zijpZJlxsDFEsYCvkBcv RTjxkHT0fenff2jJdhNjBPAAqP1hrZ5cxR9l2v4tjrsf3Nx53OvrVfrkZP3tqGFJEfWX7 b6IgoNA0uHE6tbmMQ05p3rWCl0qiat5mjQV1Ui39IfVSM5a9T4C2rA2piHyIiEPnD2DDZ 9Cm1rx7gmatyoMNvgH1RyL/8BUlyDZM7LyHTUNaoim5xH6Zv1Scw6uBlnNspOzDmEMg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794590541; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=KTJvfPm5MhrZL6PZHC7k+JPoeEuuln07SQkOE65PihU=; b=10XPNGO18wvlG6gWt6QdebDz5uQxclTqnGZkg3XP7Gm2Ip6I+s8VaRJsT2QQEd7Rkyuv ZUN4fH1hHoP41hBpiiQ/N24QBqV7/tXytZWuP9izfD0T3xSok+nHuU5GjeRwd/i3z3K9Z XNfRZfMEgc7mtOi/UaDj1VdeLOdDvfMVmLZOoOiTAhLMY9X48l8uQUKLlYz6en4CsTitd CMy7TLT/8NG+iCsqaCl4fO717Hxjp5arWj/+3MwsbhPcgSQhzQ3Gdn4o8PLQEdkmz4sec XYY54TT7tlGnWu/CVVYEB0I1cvmWHin5y7CndKNGJCmSygiFZM2Bft+GjtxBvtLx2Vg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=WU7Xv0t8; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3BE48606A893; Fri, 13 Nov 2026 17:22:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=WU7Xv0t8 Received: by smtp.kernel.org (Postfix) with ESMTPSA id C635D1F000C7; Fri, 13 Nov 2026 17:22:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794590541; bh=KTJvfPm5MhrZL6PZHC7k+JPoeEuuln07SQkOE65PihU=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=WU7Xv0t81ptHYC4jjb7kmoYY7UK33uiGcHLKQhs4E4vsOTMnh3um1XWiX+cWlX13y ZA8a36yXIpC6rzkEOQroJ5vkFDsL5tQmPAumog73tx44MTwq66JLTIsaubwQBSbXiC Fsa78Y7o00chPYPkb6V2Rx2IW+YnLegc+V1LDMNc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, sashiko-bot@kernel.org, Hari Bathini , Abhishek Dubey , Saket Kumar Bhaskar , Yeswanth Krishna Tellakula , R Nageswara Sastry , Madhavan Srinivasan , Sasha Levin Subject: [PATCH 6.18 481/686] powerpc/bpf: fix buffer overflow in JIT for large BPF programs Date: Fri, 13 Nov 2026 10:50:14 -0500 Message-ID: <20261113153837.256131186@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261113153820.902362109@linuxfoundation.org> References: <20261113153820.902362109@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Abhishek Dubey [ Upstream commit 78ce55b7913a78e1687306668e078b86bc6508ee ] During size calculation in pass-0, exit_addr is 0 since addrs[fp->len] is not yet populated. bpf_jit_emit_exit_insn() treats a zero exit_addr as in-range and skips bpf_jit_build_epilogue(), so the alternate inline epilogue instructions are not counted in alloclen. In later passes, if the real exit_addr falls outside the 32MB branch range, the full inline epilogue is emitted into the already-allocated buffer, writing past its end and corrupting adjacent memory. Fix by ensuring exit_addr is non-zero before treating it as in-range, so pass-0 always falls through to bpf_jit_build_epilogue() and conservatively accounts for all epilogue instructions in alloclen. Also range check alt_exit_addr directly in the else-if condition. Since exit_addr handling now falls through to the epilogue, two related issues in bpf_int_jit_compile() must also be addressed: 1. Reset cgctx.alt_exit_addr before the second size-calculation pass. Without this, a stale alt_exit_addr from the first pass causes the second pass to emit a single jump instead of the full epilogue, undercounting alloclen and reintroducing the overflow. 2. Recompute addrs[fp->len] at the end of each code-generation pass. The larger pass-0 body can shrink in later passes as out-of-range exits settle into in-range jumps; a stale addrs[fp->len] would leave exit branches targeting past the real (shrunken) epilogue. Because shrinkage in a later pass can move the epilogue offset, the fixed two-pass loop is no longer sufficient: an exit that was out of range in an earlier pass may fall in range once the epilogue offset shrinks, shrinking the body further and overwriting the start of the epilogue. Convert the code-generation loop to iterate until the program size converges, bounded by CODEGEN_MAX_PASSES, and fail the JIT if it does not converge. Reported-by: sashiko-bot@kernel.org Closes: https://lore.kernel.org/bpf/20260529015855.364704-2-adubey@linux.ibm.com/T/#mfcb23909d977b949727cca4f59ee56a13fd69b92 Fixes: 0ffdbce6f4a8 ("powerpc/bpf: Handle large branch ranges with BPF_EXIT") Cc: stable@vger.kernel.org Signed-off-by: Hari Bathini Signed-off-by: Abhishek Dubey Signed-off-by: Saket Kumar Bhaskar Tested-by: Yeswanth Krishna Tellakula Tested-by: R Nageswara Sastry Link: https://lore.kernel.org/bpf/20260529015855.364704-2-adubey@linux.ibm.com/T/#mfcb23909d977b949727cca4f59ee56a13fd69b92 Signed-off-by: Madhavan Srinivasan Link: https://patch.msgid.link/eebffa997e07781b384c4480e2b03c5b87c1aeb1.1789982239.git.skb99@linux.ibm.com [ sashal: Replaced goto out_err with fp = org_fp followed by goto out_addrs because the out_err label is absent. ] Signed-off-by: Sasha Levin --- arch/powerpc/net/bpf_jit.h | 7 +++++++ arch/powerpc/net/bpf_jit_comp.c | 35 +++++++++++++++++++++++++-------- 2 files changed, 34 insertions(+), 8 deletions(-) diff --git a/arch/powerpc/net/bpf_jit.h b/arch/powerpc/net/bpf_jit.h index 8334cd667bba1..ae2c92a8b6e77 100644 --- a/arch/powerpc/net/bpf_jit.h +++ b/arch/powerpc/net/bpf_jit.h @@ -14,6 +14,13 @@ #include #include +/* + * We need at least 2 passes for proper code generation, and may need + * additional passes if code size changes between passes. + */ +#define CODEGEN_MIN_PASSES 2 +#define CODEGEN_MAX_PASSES 3 + #ifdef CONFIG_PPC64_ELF_ABI_V1 #define FUNCTION_DESCR_SIZE 24 #else diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c index cedab25aa3a82..829b60ae485ff 100644 --- a/arch/powerpc/net/bpf_jit_comp.c +++ b/arch/powerpc/net/bpf_jit_comp.c @@ -99,11 +99,10 @@ void bpf_jit_build_fentry_stubs(u32 *image, struct codegen_context *ctx) int bpf_jit_emit_exit_insn(u32 *image, struct codegen_context *ctx, int tmp_reg, long exit_addr) { - if (!exit_addr || is_offset_in_branch_range(exit_addr - (ctx->idx * 4))) { + if (exit_addr && is_offset_in_branch_range(exit_addr - (long)(ctx->idx * 4))) { PPC_JMP(exit_addr); - } else if (ctx->alt_exit_addr) { - if (WARN_ON(!is_offset_in_branch_range((long)ctx->alt_exit_addr - (ctx->idx * 4)))) - return -1; + } else if (ctx->alt_exit_addr && is_offset_in_branch_range( + (long)(ctx->alt_exit_addr) - (long)(ctx->idx * 4))) { PPC_JMP(ctx->alt_exit_addr); } else { ctx->alt_exit_addr = ctx->idx * 4; @@ -223,6 +222,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp) */ if (cgctx.seen & SEEN_TAILCALL || !is_offset_in_branch_range((long)cgctx.idx * 4)) { cgctx.idx = 0; + cgctx.alt_exit_addr = 0; if (bpf_jit_build_body(fp, NULL, NULL, &cgctx, addrs, 0, false)) { fp = org_fp; goto out_addrs; @@ -259,10 +259,13 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp) code_base = (u32 *)(image + FUNCTION_DESCR_SIZE); fcode_base = (u32 *)(fimage + FUNCTION_DESCR_SIZE); - /* Code generation passes 1-2 */ - for (pass = 1; pass < 3; pass++) { + /* Code generation passes 1-2+, loop until program size converges. */ + for (pass = 1; pass <= CODEGEN_MAX_PASSES; pass++) { + u32 prev_proglen = proglen; + /* Now build the prologue, body code & epilogue for real. */ cgctx.idx = 0; + cgctx.exentry_idx = 0; cgctx.alt_exit_addr = 0; bpf_jit_build_prologue(code_base, &cgctx); if (bpf_jit_build_body(fp, code_base, fcode_base, &cgctx, addrs, pass, @@ -272,11 +275,27 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp) fp = org_fp; goto out_addrs; } + addrs[fp->len] = cgctx.idx * 4; bpf_jit_build_epilogue(code_base, &cgctx); + proglen = cgctx.idx * 4; + if (bpf_jit_enable > 1) pr_info("Pass %d: shrink = %d, seen = 0x%x\n", pass, - proglen - (cgctx.idx * 4), cgctx.seen); + prev_proglen - proglen, cgctx.seen); + + /* Check if program size has converged, but ensure minimum passes */ + if (pass >= CODEGEN_MIN_PASSES && proglen == prev_proglen) + break; + + if (pass == CODEGEN_MAX_PASSES && proglen != prev_proglen) { + pr_err("BPF JIT: Program did not converge after %d passes\n", + CODEGEN_MAX_PASSES); + bpf_arch_text_copy(&fhdr->size, &hdr->size, sizeof(hdr->size)); + bpf_jit_binary_pack_free(fhdr, hdr); + fp = org_fp; + goto out_addrs; + } } if (bpf_jit_enable > 1) @@ -336,7 +355,7 @@ int bpf_add_extable_entry(struct bpf_prog *fp, u32 *image, u32 *fimage, int pass u32 *fixup; /* Populate extable entries only in the last pass */ - if (pass != 2) + if (pass < CODEGEN_MIN_PASSES) return 0; if (!fp->aux->extable || -- 2.53.0