From c55191e96caa9d787e8f682c5e525b7f8172a3b4 Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Wed, 7 Nov 2018 11:36:20 +0100 Subject: arm64: mm: apply r/o permissions of VM areas to its linear alias as well On arm64, we use block mappings and contiguous hints to map the linear region, to minimize the TLB footprint. However, this means that the entire region is mapped using read/write permissions, which we cannot modify at page granularity without having to take intrusive measures to prevent TLB conflicts. This means the linear aliases of pages belonging to read-only mappings (executable or otherwise) in the vmalloc region are also mapped read/write, and could potentially be abused to modify things like module code, bpf JIT code or other read-only data. So let's fix this, by extending the set_memory_ro/rw routines to take the linear alias into account. The consequence of enabling this is that we can no longer use block mappings or contiguous hints, so in cases where the TLB footprint of the linear region is a bottleneck, performance may be affected. Therefore, allow this feature to be runtime en/disabled, by setting rodata=full (or 'on' to disable just this enhancement, or 'off' to disable read-only mappings for code and r/o data entirely) on the kernel command line. Also, allow the default value to be set via a Kconfig option. Tested-by: Laura Abbott Signed-off-by: Ard Biesheuvel Signed-off-by: Will Deacon --- arch/arm64/include/asm/mmu_context.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'arch/arm64/include/asm/mmu_context.h') diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h index 1e58bf58c22b..dfcfeffd2080 100644 --- a/arch/arm64/include/asm/mmu_context.h +++ b/arch/arm64/include/asm/mmu_context.h @@ -35,6 +35,8 @@ #include #include +extern bool rodata_full; + static inline void contextidr_thread_switch(struct task_struct *next) { if (!IS_ENABLED(CONFIG_PID_IN_CONTEXTIDR)) -- cgit