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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> MIME-Version: 1.0 X-Developer-Signature: v=1; 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a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 X-Stat-Signature: tekk96oowns5f67n8ffy1sm9bok9q4yg X-Rspam-User: X-Rspamd-Queue-Id: E25C41C000F X-Rspamd-Server: rspam02 X-HE-Tag: 1719003047-530360 X-HE-Meta: U2FsdGVkX1/QFVQI9+Cs7KKwNiqCw5jVFhSNwuWHubxwTSukXodi5/3ZLaUPVUJjMpGey0wzCQWb672ClwPlq8QpHRhG+6UYzc/9DFbX8fcFjGVUUSbunBG4ZTDTxoKzKm6BvMNPvTrKuzGMeRo1fybJWKwaGmHw9utDPv9kzEpIf13EN2C0zF/8vKVYor4HbZ8dBkAS4a/gKHApR53QXkKP/mGwp2eFN3VeT0QAmHvvC05m9/loZu1Wc89X2ea5MUCSibSJlAO7lh0kIhSNPad+R4JjG7rl/j53GCwA20XBZptVjUS4BPIcJdzAYPzLy2kHorcKKJANfmz/YCoKDaCI3fMmJ3V/Lf7Z8IjiCf+npVFlfhMHclCZ3/+KSfyHL6oIkoiLWT7Ltki/+//e4jovm/3c7ZWynAI2/MKV6hFwvRJ8GSCz38UlVt4l3/nzVmGraB0DGc255C0hJrLnfFxApQ3go0+Hrz0gAh7Z02A4rqSjKaG93gVfr4bF1Q+tcRwwMdV/Ni7LKA0cX1VjfkDuXgwVsTdtxFvWC+NhLuNvPgo7yE7AhE4aQD/QY6CFRZ1wKA8boMDESROupQ8mmQCpqsQQ77OgErfWBNaYYi0oPiyzBsCWXZ8J3nwtn7vnImswqjs9KENKDUGDzTs+DjKDHs5bDNO3Adcy4Th286SykC5z0dDvEY92nF41l2YTQGK/kjamu1YcSN04DNMWufe284GeJY1uNRtnWF+QAMYsVRnvK6MBNlCNKd7/g4VWh0eD0Oo0pVbDuVn93PnzYNHftMVuxdZ34eleG2SsuyoocwwI2qqsWG7tbT+dKbUiTY26GsNyqnSlE5oC/sNZe5Je5XQe4ojmW60iWyz0xV5CJ7t07lz3sQeCD/B8Y0A82jRcwn9KQCTzdS9ZpJsth157r1d1OsSX5GoU7VRtxI8yMzrdoTmBuqemWQMaZ1PRLK0yZ0H3QJr0JWC4MpD f4S1+fx0 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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,