From: Marek Bykowski marek.bykowski@gmail.com
[ Upstream commit d5e3050c0feb8bf7b9a75482fafcc31b90257926 ]
If the properties 'linux,initrd-start' and 'linux,initrd-end' of the chosen node populated from the bootloader, eg. U-Boot, are so that start > end, then the phys_initrd_size calculated from end - start is negative that subsequently gets converted to a high positive value for being unsigned long long. Then, the memory region with the (invalid) size is added to the bootmem and attempted being paged in paging_init() that results in the kernel fault.
For example, on the FVP ARM64 system I'm running, the U-Boot populates the 'linux,initrd-start' with 8800_0000 and 'linux,initrd-end' with 0. The phys_initrd_size calculated is then ffff_ffff_7800_0000 (= 0 - 8800_0000 = -8800_0000 + ULLONG_MAX + 1). paging_init() then attempts to map the address 8800_0000 + ffff_ffff_7800_0000 and oops'es as below.
It should be stressed, it is generally a fault of the bootloader's with the kernel relying on it, however we should not allow the bootloader's misconfiguration to lead to the kernel oops. Not only the kernel should be bullet proof against it but also finding the root cause of the paging fault spanning over the bootloader, DT, and kernel may happen is not so easy.
Unable to handle kernel paging request at virtual address fffffffefe43c000 Mem abort info: ESR = 0x96000007 EC = 0x25: DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 Data abort info: ISV = 0, ISS = 0x00000007 CM = 0, WnR = 0 swapper pgtable: 4k pages, 39-bit VAs, pgdp=0000000080e3d000 [fffffffefe43c000] pgd=0000000080de9003, pud=0000000080de9003 Unable to handle kernel paging request at virtual address ffffff8000de9f90 Mem abort info: ESR = 0x96000005 EC = 0x25: DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 Data abort info: ISV = 0, ISS = 0x00000005 CM = 0, WnR = 0 swapper pgtable: 4k pages, 39-bit VAs, pgdp=0000000080e3d000 [ffffff8000de9f90] pgd=0000000000000000, pud=0000000000000000 Internal error: Oops: 96000005 [#1] PREEMPT SMP Modules linked in: CPU: 0 PID: 0 Comm: swapper Not tainted 5.4.51-yocto-standard #1 Hardware name: FVP Base (DT) pstate: 60000085 (nZCv daIf -PAN -UAO) pc : show_pte+0x12c/0x1b4 lr : show_pte+0x100/0x1b4 sp : ffffffc010ce3b30 x29: ffffffc010ce3b30 x28: ffffffc010ceed80 x27: fffffffefe43c000 x26: fffffffefe43a028 x25: 0000000080bf0000 x24: 0000000000000025 x23: ffffffc010b8d000 x22: ffffffc010e3d000 x23: ffffffc010b8d000 x22: ffffffc010e3d000 x21: 0000000080de9000 x20: ffffff7f80000f90 x19: fffffffefe43c000 x18: 0000000000000030 x17: 0000000000001400 x16: 0000000000001c00 x15: ffffffc010cef1b8 x14: ffffffffffffffff x13: ffffffc010df1f40 x12: ffffffc010df1b70 x11: ffffffc010ce3b30 x10: ffffffc010ce3b30 x9 : 00000000ffffffc8 x8 : 0000000000000000 x7 : 000000000000000f x6 : ffffffc010df16e8 x5 : 0000000000000000 x4 : 0000000000000000 x3 : 00000000ffffffff x2 : 0000000000000000 x1 : 0000008080000000 x0 : ffffffc010af1d68 Call trace: show_pte+0x12c/0x1b4 die_kernel_fault+0x54/0x78 __do_kernel_fault+0x11c/0x128 do_translation_fault+0x58/0xac do_mem_abort+0x50/0xb0 el1_da+0x1c/0x90 __create_pgd_mapping+0x348/0x598 paging_init+0x3f0/0x70d0 setup_arch+0x2c0/0x5d4 start_kernel+0x94/0x49c Code: 92748eb5 900052a0 9135a000 cb010294 (f8756a96)
Signed-off-by: Marek Bykowski marek.bykowski@gmail.com Link: https://lore.kernel.org/r/20220909023358.76881-1-marek.bykowski@gmail.com Signed-off-by: Rob Herring robh@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/of/fdt.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c index 338171c978cc..bb6c517c137e 100644 --- a/drivers/of/fdt.c +++ b/drivers/of/fdt.c @@ -937,6 +937,8 @@ static void __init early_init_dt_check_for_initrd(unsigned long node) if (!prop) return; end = of_read_number(prop, len/4); + if (start > end) + return;
__early_init_dt_declare_initrd(start, end); phys_initrd_start = start;