From patchwork Fri Jun 21 20:50:43 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kees Cook X-Patchwork-Id: 13708060 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 0C3031607B3; Fri, 21 Jun 2024 20:50:46 +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=1719003047; cv=none; b=IrsYBXhtK7BjKN3mgwGof5Seib5vGtd7MVpsrfNCd4+TPpnZXz8gy3h7afE/nJxcrZcDLOAm13rd9unlrrGR5WJB/ixYftxbBpzVa98NfMSAfMTscQAnDrk5gWvyI5igddQ+xJoROMx6dDYH9DAAJH13faZPx8dDF1OXQH0UXYg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719003047; c=relaxed/simple; bh=08nbucMThJ3PA9ERR1mzxp2dFYTwOJzapfx7t7pEvKw=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=YgfL03UBUVxD5kDY/OTDx9Cly3V7/OgrN2Sc/alrrnsokwCSsC4IwoOoSRckme+YrP0rCP0wllqP1Lyvli0Yd7Y/xi3QbJib2VHH6A1E79j86gY74nqbFIF2w6EJiFOeQitUv5KsKpz1xelJaxqUtURUg49DMmuxB5GmTu71v3c= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=TLrlDt0+; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="TLrlDt0+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8D5D2C2BBFC; Fri, 21 Jun 2024 20:50:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1719003046; bh=08nbucMThJ3PA9ERR1mzxp2dFYTwOJzapfx7t7pEvKw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=TLrlDt0+nOx1CCG90R/6CZa8aFePcr7Fh/AeYwaCqHSxu5FfsfEojI7ZgaeGgtqtI 5XCG39Hh1W6x1coVzwHlQBQD6E7g+lgJfkSmFWJyyL5J33bhPIxoawQN6jHhSJI6Hv QBI0xRNJZLfAQc2iyBaGfKih6Dstk/bIcXw+cUHPQfTnnkm3tHEI0HEmstimhUuwOk o45jBz6xPL57QIXS9IXaN6Ysv7asvRwsPO9ZDLDq01zdzCogmhi2dD2Eneob3Svr/w Ao2EL1yAr4eLyMJTaqqeFfduG05K03dovRWo9UKw9U2mjglj9ZUtJEmECDfzZGC+2c E+yOfeRVfM69w== From: Kees Cook To: Guenter Roeck Cc: Kees Cook , Eric Biederman , Alexander Viro , Christian Brauner , Jan Kara , Alexey Dobriyan , Laurent Vivier , Lukas Bulwahn , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Justin Stitt , linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: [PATCH v2 1/2] execve: Keep bprm->argmin behind CONFIG_MMU Date: Fri, 21 Jun 2024 13:50:43 -0700 Message-Id: <20240621205046.4001362-1-kees@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240621204729.it.434-kees@kernel.org> References: <20240621204729.it.434-kees@kernel.org> Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3893; i=kees@kernel.org; h=from:subject; bh=08nbucMThJ3PA9ERR1mzxp2dFYTwOJzapfx7t7pEvKw=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBmdeekFSbBk2O2iHqrCrSBFtyRjbOTF4Orfwi4G NzijvpupVKJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCZnXnpAAKCRCJcvTf3G3A JhSOEACWWK0PtH8YUUh7IL6RFGs61JDtltA65r7YwqGHW9pAb9Ei2/Pm9tSrkRjjCQJJzSUlijZ sIJL7ggzsjCbCl1l/PFkcuvC6PFmLFZ9YeyqUF0a8srpivUSLRkm7rVqiJuQ+xSRJVHc29A/ugS FS6t1mFxeikcvz9vHMaqpgenvD4Mgl14Rb4oedV0SP3ZB15v8eABGMoY4cTC3Bw0mLltSXzHm0I 1gn7FNVNhFnNJFD2t/fVw/u8uwmeGIUaAEE6J33lGvlvMJbxBFp8umKg6a6w/+98mE8jSksVIoE Pok5N1XYsTDENcddKk0ZHkY6W0ux+c967CH87wD17w2K8rgr2sFGddRYxCUSU0KG7LZFu6OR9vZ /OZKQfAZCoPw0rTZrZc1H62h7goz0vPuTsovL9Z7Y9AxFyW5AcEsqI2HNvtBhqndK3yc1myJpdP 3hJY0DDp4lEyk5qjqG1/wgir84UVSO9TISyB7t0CfX8LNOXI7cJiHUd89R/UyiAhtm02dF1QHAI 8/+q/y2dgHXVv4esZytTnXmkwtm2oZU8jjiTNfSfO9/LZElw3wMeoze4TGuAhM6wwQA7n7pQDZn tRgSx5v0//uEVarmd41/WOez36Qxoaxs5W8UfR+zanBm4abpwbd21c9B+5sxEHAOmRSxj6FmFVF k5BWD3WJLC17tDg== X-Developer-Key: i=kees@kernel.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 When argmin was added in commit 655c16a8ce9c ("exec: separate MM_ANONPAGES and RLIMIT_STACK accounting"), it was intended only for validating stack limits on CONFIG_MMU[1]. All checking for reaching the limit (argmin) is wrapped in CONFIG_MMU ifdef checks, though setting argmin was not. That argmin is only supposed to be used under CONFIG_MMU was rediscovered recently[2], and I don't want to trip over this again. Move argmin's declaration into the existing CONFIG_MMU area, and add helpers functions so the MMU tests can be consolidated. Link: https://lore.kernel.org/all/20181126122307.GA1660@redhat.com [1] Link: https://lore.kernel.org/all/202406211253.7037F69@keescook/ [2] Signed-off-by: Kees Cook --- Cc: Guenter Roeck Cc: Eric Biederman Cc: Alexander Viro Cc: Christian Brauner Cc: Jan Kara Cc: Alexey Dobriyan Cc: Laurent Vivier Cc: Lukas Bulwahn Cc: linux-fsdevel@vger.kernel.org Cc: linux-mm@kvack.org --- fs/exec.c | 26 ++++++++++++++++++++------ fs/exec_test.c | 2 ++ include/linux/binfmts.h | 2 +- 3 files changed, 23 insertions(+), 7 deletions(-) diff --git a/fs/exec.c b/fs/exec.c index c3bec126505b..b7bc63bfb907 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -486,6 +486,23 @@ static int count_strings_kernel(const char *const *argv) return i; } +static inline int bprm_set_stack_limit(struct linux_binprm *bprm, + unsigned long limit) +{ +#ifdef CONFIG_MMU + bprm->argmin = bprm->p - limit; +#endif + return 0; +} +static inline bool bprm_hit_stack_limit(struct linux_binprm *bprm) +{ +#ifdef CONFIG_MMU + return bprm->p < bprm->argmin; +#else + return false; +#endif +} + /* * Calculate bprm->argmin from: * - _STK_LIM @@ -532,8 +549,7 @@ static int bprm_stack_limits(struct linux_binprm *bprm) return -E2BIG; limit -= ptr_size; - bprm->argmin = bprm->p - limit; - return 0; + return bprm_set_stack_limit(bprm, limit); } /* @@ -571,10 +587,8 @@ static int copy_strings(int argc, struct user_arg_ptr argv, pos = bprm->p; str += len; bprm->p -= len; -#ifdef CONFIG_MMU - if (bprm->p < bprm->argmin) + if (bprm_hit_stack_limit(bprm)) goto out; -#endif while (len > 0) { int offset, bytes_to_copy; @@ -649,7 +663,7 @@ int copy_string_kernel(const char *arg, struct linux_binprm *bprm) /* We're going to work our way backwards. */ arg += len; bprm->p -= len; - if (IS_ENABLED(CONFIG_MMU) && bprm->p < bprm->argmin) + if (bprm_hit_stack_limit(bprm)) return -E2BIG; while (len > 0) { diff --git a/fs/exec_test.c b/fs/exec_test.c index 32a90c6f47e7..8fea0bf0b7f5 100644 --- a/fs/exec_test.c +++ b/fs/exec_test.c @@ -96,7 +96,9 @@ static void exec_test_bprm_stack_limits(struct kunit *test) rc = bprm_stack_limits(&bprm); KUNIT_EXPECT_EQ_MSG(test, rc, result->expected_rc, "on loop %d", i); +#ifdef CONFIG_MMU KUNIT_EXPECT_EQ_MSG(test, bprm.argmin, result->expected_argmin, "on loop %d", i); +#endif } } diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h index 70f97f685bff..e6c00e860951 100644 --- a/include/linux/binfmts.h +++ b/include/linux/binfmts.h @@ -19,13 +19,13 @@ struct linux_binprm { #ifdef CONFIG_MMU struct vm_area_struct *vma; unsigned long vma_pages; + unsigned long argmin; /* rlimit marker for copy_strings() */ #else # define MAX_ARG_PAGES 32 struct page *page[MAX_ARG_PAGES]; #endif struct mm_struct *mm; unsigned long p; /* current top of mem */ - unsigned long argmin; /* rlimit marker for copy_strings() */ unsigned int /* Should an execfd be passed to userspace? */ have_execfd:1, From patchwork Fri Jun 21 20:50:44 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kees Cook X-Patchwork-Id: 13708059 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 0C277155329; Fri, 21 Jun 2024 20:50:46 +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=1719003047; cv=none; b=I53SOEJ5ZSQWaUZZrdOzfv0p9tEEAEgbqFwM477LmQMxQzHpq7DwnrEXCPk3FqA6jqD6ss/HZvMBYF1L41Uz6wsSbDCiTVa1Fd89MLaAT+2Mf++34uMcWZ6cFetGwYjl0aw0gJm9/Nzm9/DcFyjW8zvAp6mWkiwaA4bvlEWCOHE= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719003047; c=relaxed/simple; bh=HGKiztfmnXGwe57zj0+vTZfhNT7KQZ5JNN+BGrOb5Qw=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=aJhaQ1glf+X67j0PVfyP9JfMIJfAPlY3sr3Q3quEzR66u4mGqIC59xbudE2CTSr0ocejMs+egNSUyfJqalOU7bl3G5ke18SLecQxFVKnXxG55BU49qFksf/3KefZPaq0ajAXt/d2hL5iun8gHL9HYhtjZEf+AC0HH8x9KEvkGbI= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=RAkDBFKV; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="RAkDBFKV" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9F68DC4AF09; Fri, 21 Jun 2024 20:50:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1719003046; bh=HGKiztfmnXGwe57zj0+vTZfhNT7KQZ5JNN+BGrOb5Qw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=RAkDBFKVl8xmtb2DHIPOV2tWg9gbzOL1odQSCGDEXJNPgM0WUxIxBe87GtqqWJ+4A 1Ere96aP9tXLhWixhIZSvQheDU5VDOtlYZ7/DpmebD/f4Tp0apl4GBwQ0utpvwApMh KAeYFQUGf8tbr+xiQDD/fo3hDTyV18sQydUOi+eZsvrNA+K2MSdVQdGwKJLzt7ejma e3onkPPrABfNag37HD3ojtklzAwWmw5WQ/6vezXvCejKws996+3d20U3Ir7nxeBm4w kXP35UpmP8mmSxdjYJpGQhw+KveCa+Jz9gCAWSOsOHo7XrHNY/Nb/jhTL1PYPx5LyR LdVoE6OLcFbCg== From: Kees Cook To: Guenter Roeck Cc: Kees Cook , Eric Biederman , Justin Stitt , Alexander Viro , Christian Brauner , Jan Kara , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Alexey Dobriyan , Laurent Vivier , Lukas Bulwahn , linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: [PATCH v2 2/2] exec: Avoid pathological argc, envc, and bprm->p values Date: Fri, 21 Jun 2024 13:50:44 -0700 Message-Id: <20240621205046.4001362-2-kees@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240621204729.it.434-kees@kernel.org> References: <20240621204729.it.434-kees@kernel.org> Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=4831; i=kees@kernel.org; h=from:subject; bh=HGKiztfmnXGwe57zj0+vTZfhNT7KQZ5JNN+BGrOb5Qw=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBmdeekLPmeDCyHBRB+FOlnbPUxLBpaNJ4ss73+0 bFmZEGvDfSJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCZnXnpAAKCRCJcvTf3G3A JrHpEACwK/KoxBiuYpyBhT1faCVPtic/WRxA+xyHpVQqTf6/yL7eoyTCaiJk58mIoXAOB1tXoq1 89j9SqoxNE/uRUHLli/HOj4QYrwLyzyr6XqxRj2hwij6HLNf9poM46hOJ/Zz5tgjL9EPkZDam3/ 7aK6+OHKWEWWqqlzQhmmla+vhcKlA8MMZ2t1InXPiiXw/htTp52e2IHC0W0q4rubg+6sihRa36e Ov/Pa6O58b1fG2Ik8GcjDXlBSTj3uaTNcSZOxvZg10WpPs5r2y01iBcT+N3IHSJUFmFWpiksvKT btcLB7+7FHVBvjMKcTSA9+5TytPgMiyVMN78mKTyEfkJEjWE7GRAbeVWYTPGR0giV+lV4WJ/JJK ovljU3VUetF/2fEn8Dpr8cXSNetg15795IqzDIgO0A6FDrGGHkkXF/+q0yk3Q3JMGliylAZitXC 40+5rkqqddWDwsVg+qkKqsJrx5ttQXSi+EpAhDb62nFUtbmuznNzMEwVJgfykpWhhHMsuad13G9 DKiPCY7OeiiKNbXjfgkXID2BkHtEj1kJRD6fEVkiFuDBzqD6qWDhwLCS/mv4q5u9hLpGs68pywr ivAMmlI7v7KA3pttOS+oPQea7JkKuqHV096jHTtskEhpy9PH9bGkfGeC2PLQuBjKAZ2VF2FT6Wx jsCjqkqW7b/2erQ== X-Developer-Key: i=kees@kernel.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Make sure nothing goes wrong with the string counters or the bprm's belief about the stack pointer. Add checks and matching self-tests. Take special care for !CONFIG_MMU, since argmin is not exposed there. For 32-bit validation, 32-bit UML was used: $ tools/testing/kunit/kunit.py run \ --make_options CROSS_COMPILE=i686-linux-gnu- \ --make_options SUBARCH=i386 \ exec For !MMU validation, m68k was used: $ tools/testing/kunit/kunit.py run \ --arch m68k --make_option CROSS_COMPILE=m68k-linux-gnu- \ exec Link: https://lore.kernel.org/r/20240520021615.741800-2-keescook@chromium.org Signed-off-by: Kees Cook --- Cc: Guenter Roeck Cc: Eric Biederman Cc: Justin Stitt Cc: Alexander Viro Cc: Christian Brauner Cc: Jan Kara Cc: linux-fsdevel@vger.kernel.org Cc: linux-mm@kvack.org --- fs/exec.c | 10 +++++++++- fs/exec_test.c | 28 +++++++++++++++++++++++++++- 2 files changed, 36 insertions(+), 2 deletions(-) diff --git a/fs/exec.c b/fs/exec.c index b7bc63bfb907..5b580ff8d955 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -490,6 +490,9 @@ static inline int bprm_set_stack_limit(struct linux_binprm *bprm, unsigned long limit) { #ifdef CONFIG_MMU + /* Avoid a pathological bprm->p. */ + if (bprm->p < limit) + return -E2BIG; bprm->argmin = bprm->p - limit; #endif return 0; @@ -531,6 +534,9 @@ static int bprm_stack_limits(struct linux_binprm *bprm) * of argument strings even with small stacks */ limit = max_t(unsigned long, limit, ARG_MAX); + /* Reject totally pathological counts. */ + if (bprm->argc < 0 || bprm->envc < 0) + return -E2BIG; /* * We must account for the size of all the argv and envp pointers to * the argv and envp strings, since they will also take up space in @@ -544,7 +550,9 @@ static int bprm_stack_limits(struct linux_binprm *bprm) * argc can never be 0, to keep them from walking envp by accident. * See do_execveat_common(). */ - ptr_size = (max(bprm->argc, 1) + bprm->envc) * sizeof(void *); + if (check_add_overflow(max(bprm->argc, 1), bprm->envc, &ptr_size) || + check_mul_overflow(ptr_size, sizeof(void *), &ptr_size)) + return -E2BIG; if (limit <= ptr_size) return -E2BIG; limit -= ptr_size; diff --git a/fs/exec_test.c b/fs/exec_test.c index 8fea0bf0b7f5..7c77d039680b 100644 --- a/fs/exec_test.c +++ b/fs/exec_test.c @@ -8,9 +8,34 @@ struct bprm_stack_limits_result { }; static const struct bprm_stack_limits_result bprm_stack_limits_results[] = { - /* Giant values produce -E2BIG */ + /* Negative argc/envc counts produce -E2BIG */ + { { .p = ULONG_MAX, .rlim_stack.rlim_cur = ULONG_MAX, + .argc = INT_MIN, .envc = INT_MIN }, .expected_rc = -E2BIG }, + { { .p = ULONG_MAX, .rlim_stack.rlim_cur = ULONG_MAX, + .argc = 5, .envc = -1 }, .expected_rc = -E2BIG }, + { { .p = ULONG_MAX, .rlim_stack.rlim_cur = ULONG_MAX, + .argc = -1, .envc = 10 }, .expected_rc = -E2BIG }, + /* The max value of argc or envc is MAX_ARG_STRINGS. */ { { .p = ULONG_MAX, .rlim_stack.rlim_cur = ULONG_MAX, .argc = INT_MAX, .envc = INT_MAX }, .expected_rc = -E2BIG }, + { { .p = ULONG_MAX, .rlim_stack.rlim_cur = ULONG_MAX, + .argc = MAX_ARG_STRINGS, .envc = MAX_ARG_STRINGS }, .expected_rc = -E2BIG }, + { { .p = ULONG_MAX, .rlim_stack.rlim_cur = ULONG_MAX, + .argc = 0, .envc = MAX_ARG_STRINGS }, .expected_rc = -E2BIG }, + { { .p = ULONG_MAX, .rlim_stack.rlim_cur = ULONG_MAX, + .argc = MAX_ARG_STRINGS, .envc = 0 }, .expected_rc = -E2BIG }, + /* + * On 32-bit system these argc and envc counts, while likely impossible + * to represent within the associated TASK_SIZE, could overflow the + * limit calculation, and bypass the ptr_size <= limit check. + */ + { { .p = ULONG_MAX, .rlim_stack.rlim_cur = ULONG_MAX, + .argc = 0x20000001, .envc = 0x20000001 }, .expected_rc = -E2BIG }, +#ifdef CONFIG_MMU + /* Make sure a pathological bprm->p doesn't cause an overflow. */ + { { .p = sizeof(void *), .rlim_stack.rlim_cur = ULONG_MAX, + .argc = 10, .envc = 10 }, .expected_rc = -E2BIG }, +#endif /* * 0 rlim_stack will get raised to ARG_MAX. With 1 string pointer, * we should see p - ARG_MAX + sizeof(void *). @@ -88,6 +113,7 @@ static void exec_test_bprm_stack_limits(struct kunit *test) /* Double-check the constants. */ KUNIT_EXPECT_EQ(test, _STK_LIM, SZ_8M); KUNIT_EXPECT_EQ(test, ARG_MAX, 32 * SZ_4K); + KUNIT_EXPECT_EQ(test, MAX_ARG_STRINGS, 0x7FFFFFFF); for (int i = 0; i < ARRAY_SIZE(bprm_stack_limits_results); i++) { const struct bprm_stack_limits_result *result = &bprm_stack_limits_results[i];