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260364d112
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
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| .. | ||
| boot | ||
| common | ||
| configs | ||
| crypto | ||
| include | ||
| kernel | ||
| lib | ||
| mach-actions | ||
| mach-airoha | ||
| mach-alpine | ||
| mach-artpec | ||
| mach-asm9260 | ||
| mach-aspeed | ||
| mach-at91 | ||
| mach-axxia | ||
| mach-bcm | ||
| mach-berlin | ||
| mach-clps711x | ||
| mach-cns3xxx | ||
| mach-davinci | ||
| mach-digicolor | ||
| mach-dove | ||
| mach-ep93xx | ||
| mach-exynos | ||
| mach-footbridge | ||
| mach-gemini | ||
| mach-highbank | ||
| mach-hisi | ||
| mach-imx | ||
| mach-integrator | ||
| mach-iop32x | ||
| mach-ixp4xx | ||
| mach-keystone | ||
| mach-lpc18xx | ||
| mach-lpc32xx | ||
| mach-mediatek | ||
| mach-meson | ||
| mach-milbeaut | ||
| mach-mmp | ||
| mach-moxart | ||
| mach-mstar | ||
| mach-mv78xx0 | ||
| mach-mvebu | ||
| mach-mxs | ||
| mach-nomadik | ||
| mach-npcm | ||
| mach-nspire | ||
| mach-omap1 | ||
| mach-omap2 | ||
| mach-orion5x | ||
| mach-oxnas | ||
| mach-pxa | ||
| mach-qcom | ||
| mach-rda | ||
| mach-realtek | ||
| mach-realview | ||
| mach-rockchip | ||
| mach-rpc | ||
| mach-s3c | ||
| mach-s5pv210 | ||
| mach-sa1100 | ||
| mach-shmobile | ||
| mach-socfpga | ||
| mach-spear | ||
| mach-sti | ||
| mach-stm32 | ||
| mach-sunxi | ||
| mach-tegra | ||
| mach-uniphier | ||
| mach-ux500 | ||
| mach-versatile | ||
| mach-vexpress | ||
| mach-vt8500 | ||
| mach-zynq | ||
| mm | ||
| net | ||
| nwfpe | ||
| plat-omap | ||
| plat-orion | ||
| plat-pxa | ||
| plat-versatile | ||
| probes | ||
| tools | ||
| vdso | ||
| vfp | ||
| xen | ||
| Kbuild | ||
| Kconfig | ||
| Kconfig-nommu | ||
| Kconfig.assembler | ||
| Kconfig.debug | ||
| Makefile | ||