6.1-stable review patch. If anyone has any objections, please let me know.
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From: Ard Biesheuvel ardb+git@google.com
From: Ard Biesheuvel ardb@kernel.org
[ Commit 2f77465b05b1270c832b5e2ee27037672ad2a10a upstream ]
The EFI stub's kernel placement logic randomizes the physical placement of the kernel by taking all available memory into account, and picking a region at random, based on a random seed.
When KASLR is disabled, this seed is set to 0x0, and this results in the lowest available region of memory to be selected for loading the kernel, even if this is below LOAD_PHYSICAL_ADDR. Some of this memory is typically reserved for the GFP_DMA region, to accommodate masters that can only access the first 16 MiB of system memory.
Even if such devices are rare these days, we may still end up with a warning in the kernel log, as reported by Tom:
swapper/0: page allocation failure: order:10, mode:0xcc1(GFP_KERNEL|GFP_DMA), nodemask=(null),cpuset=/,mems_allowed=0
Fix this by tweaking the random allocation logic to accept a low bound on the placement, and set it to LOAD_PHYSICAL_ADDR.
Fixes: a1b87d54f4e4 ("x86/efistub: Avoid legacy decompressor when doing EFI boot") Reported-by: Tom Englund tomenglund26@gmail.com Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218404 Signed-off-by: Ard Biesheuvel ardb@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/firmware/efi/libstub/arm64-stub.c | 2 +- drivers/firmware/efi/libstub/efistub.h | 3 ++- drivers/firmware/efi/libstub/randomalloc.c | 12 +++++++----- drivers/firmware/efi/libstub/x86-stub.c | 1 + 4 files changed, 11 insertions(+), 7 deletions(-)
--- a/drivers/firmware/efi/libstub/arm64-stub.c +++ b/drivers/firmware/efi/libstub/arm64-stub.c @@ -181,7 +181,7 @@ efi_status_t handle_kernel_image(unsigne */ status = efi_random_alloc(*reserve_size, min_kimg_align, reserve_addr, phys_seed, - EFI_LOADER_CODE, EFI_ALLOC_LIMIT); + EFI_LOADER_CODE, 0, EFI_ALLOC_LIMIT); if (status != EFI_SUCCESS) efi_warn("efi_random_alloc() failed: 0x%lx\n", status); } else { --- a/drivers/firmware/efi/libstub/efistub.h +++ b/drivers/firmware/efi/libstub/efistub.h @@ -906,7 +906,8 @@ efi_status_t efi_get_random_bytes(unsign
efi_status_t efi_random_alloc(unsigned long size, unsigned long align, unsigned long *addr, unsigned long random_seed, - int memory_type, unsigned long alloc_limit); + int memory_type, unsigned long alloc_min, + unsigned long alloc_max);
efi_status_t efi_random_get_seed(void);
--- a/drivers/firmware/efi/libstub/randomalloc.c +++ b/drivers/firmware/efi/libstub/randomalloc.c @@ -17,7 +17,7 @@ static unsigned long get_entry_num_slots(efi_memory_desc_t *md, unsigned long size, unsigned long align_shift, - u64 alloc_limit) + u64 alloc_min, u64 alloc_max) { unsigned long align = 1UL << align_shift; u64 first_slot, last_slot, region_end; @@ -30,11 +30,11 @@ static unsigned long get_entry_num_slots return 0;
region_end = min(md->phys_addr + md->num_pages * EFI_PAGE_SIZE - 1, - alloc_limit); + alloc_max); if (region_end < size) return 0;
- first_slot = round_up(md->phys_addr, align); + first_slot = round_up(max(md->phys_addr, alloc_min), align); last_slot = round_down(region_end - size + 1, align);
if (first_slot > last_slot) @@ -56,7 +56,8 @@ efi_status_t efi_random_alloc(unsigned l unsigned long *addr, unsigned long random_seed, int memory_type, - unsigned long alloc_limit) + unsigned long alloc_min, + unsigned long alloc_max) { unsigned long total_slots = 0, target_slot; unsigned long total_mirrored_slots = 0; @@ -78,7 +79,8 @@ efi_status_t efi_random_alloc(unsigned l efi_memory_desc_t *md = (void *)map->map + map_offset; unsigned long slots;
- slots = get_entry_num_slots(md, size, ilog2(align), alloc_limit); + slots = get_entry_num_slots(md, size, ilog2(align), alloc_min, + alloc_max); MD_NUM_SLOTS(md) = slots; total_slots += slots; if (md->attribute & EFI_MEMORY_MORE_RELIABLE) --- a/drivers/firmware/efi/libstub/x86-stub.c +++ b/drivers/firmware/efi/libstub/x86-stub.c @@ -785,6 +785,7 @@ static efi_status_t efi_decompress_kerne
status = efi_random_alloc(alloc_size, CONFIG_PHYSICAL_ALIGN, &addr, seed[0], EFI_LOADER_CODE, + LOAD_PHYSICAL_ADDR, EFI_X86_KERNEL_ALLOC_LIMIT); if (status != EFI_SUCCESS) return status;