Hi Greg,

On Mon, May 16, 2022 at 10:16:58AM +0200, gregkh@linuxfoundation.org wrote:

The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

The patch below applies to 5.10.y and 5.4.y.

As for 4.19.y and older kernels, the issue this patch fixes won't reproduce because these kernels don't have backports of pfn_valid() implementation.

From c52469701a0d3f8d8805794f75d8fd135f580010 Mon Sep 17 00:00:00 2001 From: Mike Rapoport rppt@linux.ibm.com Date: Sun, 24 Apr 2022 20:05:57 +0300 Subject: [PATCH] arm[64]/memremap: don't abuse pfn_valid() to ensure presence of linear map

The semantics of pfn_valid() is to check presence of the memory map for a PFN and not whether a PFN is covered by the linear map. The memory map may be present for NOMAP memory regions, but they won't be mapped in the linear mapping. Accessing such regions via __va() when they are memremap()'ed will cause a crash.

On v5.4.y the crash happens on qemu-arm with UEFI [1]:

<1>[ 0.084476] 8<--- cut here --- <1>[ 0.084595] Unable to handle kernel paging request at virtual address dfb76000 <1>[ 0.084938] pgd = (ptrval) <1>[ 0.085038] [dfb76000] *pgd=5f7fe801, *pte=00000000, *ppte=00000000

...

<4>[ 0.093923] [<c0ed6ce8>] (memcpy) from [<c16a06f8>] (dmi_setup+0x60/0x418) <4>[ 0.094204] [<c16a06f8>] (dmi_setup) from [<c16a38d4>] (arm_dmi_init+0x8/0x10) <4>[ 0.094408] [<c16a38d4>] (arm_dmi_init) from [<c0302e9c>] (do_one_initcall+0x50/0x228) <4>[ 0.094619] [<c0302e9c>] (do_one_initcall) from [<c16011e4>] (kernel_init_freeable+0x15c/0x1f8) <4>[ 0.094841] [<c16011e4>] (kernel_init_freeable) from [<c0f028cc>] (kernel_init+0x8/0x10c) <4>[ 0.095057] [<c0f028cc>] (kernel_init) from [<c03010e8>] (ret_from_fork+0x14/0x2c)

On kernels v5.10.y and newer the same crash won't reproduce on ARM because commit b10d6bca8720 ("arch, drivers: replace for_each_membock() with for_each_mem_range()") changed the way memory regions are registered in the resource tree, but that merely covers up the problem.

On ARM64 memory resources registered in yet another way and there the issue of wrong usage of pfn_valid() to ensure availability of the linear map is also covered.

Implement arch_memremap_can_ram_remap() on ARM and ARM64 to prevent access to NOMAP regions via the linear mapping in memremap().

Link: https://lore.kernel.org/all/Yl65zxGgFzF1Okac@sirena.org.uk Reported-by: "kernelci.org bot" bot@kernelci.org Tested-by: Mark Brown broonie@kernel.org Cc: stable@vger.kernel.org # 5.4+ Signed-off-by: Mike Rapoport rppt@linux.ibm.com --- arch/arm/include/asm/io.h | 3 +++ arch/arm/mm/ioremap.c | 8 ++++++++ arch/arm64/include/asm/io.h | 4 ++++ arch/arm64/mm/ioremap.c | 9 +++++++++ 4 files changed, 24 insertions(+)

diff --git a/arch/arm/include/asm/io.h b/arch/arm/include/asm/io.h index 7a0596fcb2e7..3cc0f6d50883 100644 --- a/arch/arm/include/asm/io.h +++ b/arch/arm/include/asm/io.h @@ -457,6 +457,9 @@ extern void pci_iounmap(struct pci_dev *dev, void __iomem *addr); extern int valid_phys_addr_range(phys_addr_t addr, size_t size); extern int valid_mmap_phys_addr_range(unsigned long pfn, size_t size); extern int devmem_is_allowed(unsigned long pfn); +extern bool arch_memremap_can_ram_remap(resource_size_t offset, size_t size, + unsigned long flags); +#define arch_memremap_can_ram_remap arch_memremap_can_ram_remap #endif

/* diff --git a/arch/arm/mm/ioremap.c b/arch/arm/mm/ioremap.c index 513c26b46db3..841b66515b37 100644 --- a/arch/arm/mm/ioremap.c +++ b/arch/arm/mm/ioremap.c @@ -500,3 +500,11 @@ void __init early_ioremap_init(void) { early_ioremap_setup(); } + +bool arch_memremap_can_ram_remap(resource_size_t offset, size_t size, + unsigned long flags) +{ + unsigned long pfn = PHYS_PFN(offset); + + return memblock_is_map_memory(pfn); +} diff --git a/arch/arm64/include/asm/io.h b/arch/arm64/include/asm/io.h index 323cb306bd28..8ac55ff3094a 100644 --- a/arch/arm64/include/asm/io.h +++ b/arch/arm64/include/asm/io.h @@ -204,4 +204,8 @@ extern int valid_mmap_phys_addr_range(unsigned long pfn, size_t size);

extern int devmem_is_allowed(unsigned long pfn);

+extern bool arch_memremap_can_ram_remap(resource_size_t offset, size_t size, + unsigned long flags); +#define arch_memremap_can_ram_remap arch_memremap_can_ram_remap + #endif /* __ASM_IO_H */ diff --git a/arch/arm64/mm/ioremap.c b/arch/arm64/mm/ioremap.c index 9be71bee902c..8dac7fcfb4bd 100644 --- a/arch/arm64/mm/ioremap.c +++ b/arch/arm64/mm/ioremap.c @@ -13,6 +13,7 @@ #include <linux/mm.h> #include <linux/vmalloc.h> #include <linux/io.h> +#include <linux/memblock.h>

#include <asm/fixmap.h> #include <asm/tlbflush.h> @@ -100,3 +101,11 @@ void __init early_ioremap_init(void) { early_ioremap_setup(); } + +bool arch_memremap_can_ram_remap(resource_size_t offset, size_t size, + unsigned long flags) +{ + unsigned long pfn = PHYS_PFN(offset); + + return memblock_is_map_memory(pfn); +}