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Tue, 12 Sep 2023 07:19:40 -0700 (PDT) Date: Tue, 12 Sep 2023 14:16:50 +0000 In-Reply-To: <20230912141549.278777-63-ardb@google.com> Mime-Version: 1.0 References: <20230912141549.278777-63-ardb@google.com> X-Developer-Key: i=ardb@kernel.org; a=openpgp; fpr=F43D03328115A198C90016883D200E9CA6329909 X-Developer-Signature: v=1; a=openpgp-sha256; l=1750; i=ardb@kernel.org; h=from:subject; bh=pu/U7f4DkZFTkoG+/EW/geTfpkkMEHP2k/cuZkS2X7Y=; b=owGbwMvMwCFmkMcZplerG8N4Wi2JIZWh6KoAT06TaNtSMZY+MwtF32OVUhn891yvXZVoD813z HP/vqSjlIVBjINBVkyRRWD233c7T0+UqnWeJQszh5UJZAgDF6cATIS5mpFhzcN7ak/TZjHx1vg9 PTlTJHRdbsAhq7nmT+6uDZhw4k7pY4Z/5v82/sjbZ3Pjx9l1ZbE12wVDxWT/5i9uWHcnKt7/1cs sdgA= X-Mailer: git-send-email 2.42.0.283.g2d96d420d3-goog Message-ID: <20230912141549.278777-123-ardb@google.com> Subject: [PATCH v4 60/61] mm: add arch hook to validate mmap() prot flags From: Ard Biesheuvel To: linux-arm-kernel@lists.infradead.org Cc: Ard Biesheuvel , Catalin Marinas , Will Deacon , Marc Zyngier , Mark Rutland , Ryan Roberts , Anshuman Khandual , Kees Cook , Joey Gouly X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230912_071943_769681_25AB3CB3 X-CRM114-Status: GOOD ( 14.16 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org From: Ard Biesheuvel Add a hook to permit architectures to perform validation on the prot flags passed to mmap(), like arch_validate_prot() does for mprotect(). This will be used by arm64 to reject PROT_WRITE+PROT_EXEC mappings on configurations that run with WXN enabled. Reviewed-by: Kees Cook Signed-off-by: Ard Biesheuvel --- include/linux/mman.h | 15 +++++++++++++++ mm/mmap.c | 3 +++ 2 files changed, 18 insertions(+) diff --git a/include/linux/mman.h b/include/linux/mman.h index 40d94411d492..f5d8c714b4bd 100644 --- a/include/linux/mman.h +++ b/include/linux/mman.h @@ -124,6 +124,21 @@ static inline bool arch_validate_flags(unsigned long flags) #define arch_validate_flags arch_validate_flags #endif +#ifndef arch_validate_mmap_prot +/* + * This is called from mmap(), which ignores unknown prot bits so the default + * is to accept anything. + * + * Returns true if the prot flags are valid + */ +static inline bool arch_validate_mmap_prot(unsigned long prot, + unsigned long addr) +{ + return true; +} +#define arch_validate_mmap_prot arch_validate_mmap_prot +#endif + /* * Optimisation macro. It is equivalent to: * (x & bit1) ? bit2 : 0 diff --git a/mm/mmap.c b/mm/mmap.c index b56a7f0c9f85..8dcd3f87063b 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1204,6 +1204,9 @@ unsigned long do_mmap(struct file *file, unsigned long addr, if (!(file && path_noexec(&file->f_path))) prot |= PROT_EXEC; + if (!arch_validate_mmap_prot(prot, addr)) + return -EACCES; + /* force arch specific MAP_FIXED handling in get_unmapped_area */ if (flags & MAP_FIXED_NOREPLACE) flags |= MAP_FIXED;