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| author | Ard Biesheuvel <ardb@kernel.org> | 2024-01-25 16:32:07 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2024-04-10 17:38:23 +0300 |
| commit | 70a2425a1335c130dc447b8e6eb2c173d247a0b4 (patch) | |
| tree | 2671f2c23fb3ecc2826dbca093ff95064d216908 /arch | |
| parent | 4947db8687e636427f1398076cf46283989feb7e (diff) | |
| download | linux-70a2425a1335c130dc447b8e6eb2c173d247a0b4.tar.xz | |
x86/efistub: Remap kernel text read-only before dropping NX attribute
commit 9c55461040a9264b7e44444c53d26480b438eda6 upstream.
Currently, the EFI stub invokes the EFI memory attributes protocol to
strip any NX restrictions from the entire loaded kernel, resulting in
all code and data being mapped read-write-execute.
The point of the EFI memory attributes protocol is to remove the need
for all memory allocations to be mapped with both write and execute
permissions by default, and make it the OS loader's responsibility to
transition data mappings to code mappings where appropriate.
Even though the UEFI specification does not appear to leave room for
denying memory attribute changes based on security policy, let's be
cautious and avoid relying on the ability to create read-write-execute
mappings. This is trivially achievable, given that the amount of kernel
code executing via the firmware's 1:1 mapping is rather small and
limited to the .head.text region. So let's drop the NX restrictions only
on that subregion, but not before remapping it as read-only first.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/boot/compressed/Makefile | 2 | ||||
| -rw-r--r-- | arch/x86/boot/compressed/misc.c | 1 | ||||
| -rw-r--r-- | arch/x86/include/asm/boot.h | 1 |
3 files changed, 3 insertions, 1 deletions
diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile index f19c038409aa..e9522c6893be 100644 --- a/arch/x86/boot/compressed/Makefile +++ b/arch/x86/boot/compressed/Makefile @@ -84,7 +84,7 @@ LDFLAGS_vmlinux += -T hostprogs := mkpiggy HOST_EXTRACFLAGS += -I$(srctree)/tools/include -sed-voffset := -e 's/^\([0-9a-fA-F]*\) [ABCDGRSTVW] \(_text\|__bss_start\|_end\)$$/\#define VO_\2 _AC(0x\1,UL)/p' +sed-voffset := -e 's/^\([0-9a-fA-F]*\) [ABCDGRSTVW] \(_text\|__start_rodata\|__bss_start\|_end\)$$/\#define VO_\2 _AC(0x\1,UL)/p' quiet_cmd_voffset = VOFFSET $@ cmd_voffset = $(NM) $< | sed -n $(sed-voffset) > $@ diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c index 6c5c190a4d86..ee0fac468e7f 100644 --- a/arch/x86/boot/compressed/misc.c +++ b/arch/x86/boot/compressed/misc.c @@ -330,6 +330,7 @@ static size_t parse_elf(void *output) return ehdr.e_entry - LOAD_PHYSICAL_ADDR; } +const unsigned long kernel_text_size = VO___start_rodata - VO__text; const unsigned long kernel_total_size = VO__end - VO__text; static u8 boot_heap[BOOT_HEAP_SIZE] __aligned(4); diff --git a/arch/x86/include/asm/boot.h b/arch/x86/include/asm/boot.h index a38cc0afc90a..a3e0be0470a4 100644 --- a/arch/x86/include/asm/boot.h +++ b/arch/x86/include/asm/boot.h @@ -81,6 +81,7 @@ #ifndef __ASSEMBLY__ extern unsigned int output_len; +extern const unsigned long kernel_text_size; extern const unsigned long kernel_total_size; unsigned long decompress_kernel(unsigned char *outbuf, unsigned long virt_addr, |