From 3cb4a4827596abc82e55b80364f509d0fefc3051 Mon Sep 17 00:00:00 2001 From: "KONDO KAZUMA(近藤　和真)" Date: Fri, 22 Mar 2024 10:47:02 +0000 Subject: efi/libstub: fix efi_random_alloc() to allocate memory at alloc_min or higher address Following warning is sometimes observed while booting my servers: [ 3.594838] DMA: preallocated 4096 KiB GFP_KERNEL pool for atomic allocations [ 3.602918] swapper/0: page allocation failure: order:10, mode:0xcc1(GFP_KERNEL|GFP_DMA), nodemask=(null),cpuset=/,mems_allowed=0-1 ... [ 3.851862] DMA: preallocated 1024 KiB GFP_KERNEL|GFP_DMA pool for atomic allocation If 'nokaslr' boot option is set, the warning always happens. On x86, ZONE_DMA is small zone at the first 16MB of physical address space. When this problem happens, most of that space seems to be used by decompressed kernel. Thereby, there is not enough space at DMA_ZONE to meet the request of DMA pool allocation. The commit 2f77465b05b1 ("x86/efistub: Avoid placing the kernel below LOAD_PHYSICAL_ADDR") tried to fix this problem by introducing lower bound of allocation. But the fix is not complete. efi_random_alloc() allocates pages by following steps. 1. Count total available slots ('total_slots') 2. Select a slot ('target_slot') to allocate randomly 3. Calculate a starting address ('target') to be included target_slot 4. Allocate pages, which starting address is 'target' In step 1, 'alloc_min' is used to offset the starting address of memory chunk. But in step 3 'alloc_min' is not considered at all. As the result, 'target' can be miscalculated and become lower than 'alloc_min'. When KASLR is disabled, 'target_slot' is always 0 and the problem happens everytime if the EFI memory map of the system meets the condition. Fix this problem by calculating 'target' considering 'alloc_min'. Cc: linux-efi@vger.kernel.org Cc: Tom Englund Cc: linux-kernel@vger.kernel.org Fixes: 2f77465b05b1 ("x86/efistub: Avoid placing the kernel below LOAD_PHYSICAL_ADDR") Signed-off-by: Kazuma Kondo Signed-off-by: Ard Biesheuvel --- drivers/firmware/efi/libstub/randomalloc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/firmware/efi/libstub/randomalloc.c b/drivers/firmware/efi/libstub/randomalloc.c index 4e96a855fdf47..7e18528595502 100644 --- a/drivers/firmware/efi/libstub/randomalloc.c +++ b/drivers/firmware/efi/libstub/randomalloc.c @@ -120,7 +120,7 @@ efi_status_t efi_random_alloc(unsigned long size, continue; } - target = round_up(md->phys_addr, align) + target_slot * align; + target = round_up(max(md->phys_addr, alloc_min), align) + target_slot * align; pages = size / EFI_PAGE_SIZE; status = efi_bs_call(allocate_pages, EFI_ALLOCATE_ADDRESS, -- cgit 1.2.3-korg