6.6-stable review patch. If anyone has any objections, please let me know.
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From: Will Deacon will@kernel.org
[ Upstream commit acfa60dbe03802d6afd28401aa47801270e82021 ]
When CONFIG_RODATA_FULL_DEFAULT_ENABLED=y, passing "rodata=on" on the kernel command-line (rather than "rodata=full") should turn off the "full" behaviour, leaving writable linear aliases of read-only kernel memory. Unfortunately, the option has no effect in this situation and the only way to disable the "rodata=full" behaviour is to disable rodata protection entirely by passing "rodata=off".
Fix this by parsing the "on" and "off" options in the arch code, additionally enforcing that 'rodata_full' cannot be set without also setting 'rodata_enabled', allowing us to simplify a couple of checks in the process.
Fixes: 2e8cff0a0eee ("arm64: fix rodata=full") Cc: Ard Biesheuvel ardb@kernel.org Cc: Mark Rutland mark.rutland@arm.com Signed-off-by: Will Deacon will@kernel.org Reviewed-by: "Russell King (Oracle)" rmk+kernel@armlinux.org.uk Reviewed-by: Ard Biesheuvel ardb@kernel.org Link: https://lore.kernel.org/r/20231117131422.29663-1-will@kernel.org Signed-off-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/arm64/include/asm/setup.h | 17 +++++++++++++++-- arch/arm64/mm/pageattr.c | 7 +++---- 2 files changed, 18 insertions(+), 6 deletions(-)
diff --git a/arch/arm64/include/asm/setup.h b/arch/arm64/include/asm/setup.h index f4af547ef54ca..2e4d7da74fb87 100644 --- a/arch/arm64/include/asm/setup.h +++ b/arch/arm64/include/asm/setup.h @@ -21,9 +21,22 @@ static inline bool arch_parse_debug_rodata(char *arg) extern bool rodata_enabled; extern bool rodata_full;
- if (arg && !strcmp(arg, "full")) { + if (!arg) + return false; + + if (!strcmp(arg, "full")) { + rodata_enabled = rodata_full = true; + return true; + } + + if (!strcmp(arg, "off")) { + rodata_enabled = rodata_full = false; + return true; + } + + if (!strcmp(arg, "on")) { rodata_enabled = true; - rodata_full = true; + rodata_full = false; return true; }
diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c index 8e2017ba5f1b1..924843f1f661b 100644 --- a/arch/arm64/mm/pageattr.c +++ b/arch/arm64/mm/pageattr.c @@ -29,8 +29,8 @@ bool can_set_direct_map(void) * * KFENCE pool requires page-granular mapping if initialized late. */ - return (rodata_enabled && rodata_full) || debug_pagealloc_enabled() || - arm64_kfence_can_set_direct_map(); + return rodata_full || debug_pagealloc_enabled() || + arm64_kfence_can_set_direct_map(); }
static int change_page_range(pte_t *ptep, unsigned long addr, void *data) @@ -105,8 +105,7 @@ static int change_memory_common(unsigned long addr, int numpages, * If we are manipulating read-only permissions, apply the same * change to the linear mapping of the pages that back this VM area. */ - if (rodata_enabled && - rodata_full && (pgprot_val(set_mask) == PTE_RDONLY || + if (rodata_full && (pgprot_val(set_mask) == PTE_RDONLY || pgprot_val(clear_mask) == PTE_RDONLY)) { for (i = 0; i < area->nr_pages; i++) { __change_memory_common((u64)page_address(area->pages[i]),