From: Nicolas Boichat drinkcat@chromium.org
[ Upstream commit 8a5a75e5e9e55de1cef5d83ca3589cb4899193ef ]
If the device tree is incorrectly configured, and attempts to define a "no-map" reserved memory that overlaps with the kernel data/code, the kernel would crash quickly after boot, with no obvious clue about the nature of the issue.
For example, this would happen if we have the kernel mapped at these addresses (from /proc/iomem): 40000000-41ffffff : System RAM 40080000-40dfffff : Kernel code 40e00000-411fffff : reserved 41200000-413e0fff : Kernel data
And we declare a no-map shared-dma-pool region at a fixed address within that range: mem_reserved: mem_region { compatible = "shared-dma-pool"; reg = <0 0x40000000 0 0x01A00000>; no-map; };
To fix this, when removing memory regions at early boot (which is what "no-map" regions do), we need to make sure that the memory is not already reserved. If we do, __reserved_mem_reserve_reg will throw an error: [ 0.000000] OF: fdt: Reserved memory: failed to reserve memory for node 'mem_region': base 0x0000000040000000, size 26 MiB and the code that will try to use the region should also fail, later on.
We do not do anything for non-"no-map" regions, as memblock explicitly allows reserved regions to overlap, and the commit that this fixes removed the check for that precise reason.
[ qperret: fixed conflicts caused by the usage of memblock_mark_nomap ]
Fixes: 094cb98179f19b7 ("of/fdt: memblock_reserve /memreserve/ regions in the case of partial overlap") Signed-off-by: Nicolas Boichat drinkcat@chromium.org Reviewed-by: Stephen Boyd swboyd@chromium.org Signed-off-by: Quentin Perret qperret@google.com Link: https://lore.kernel.org/r/20210115114544.1830068-3-qperret@google.com Signed-off-by: Rob Herring robh@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/of/fdt.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c index e4d4a1e7ef7e2..f2e697000b96f 100644 --- a/drivers/of/fdt.c +++ b/drivers/of/fdt.c @@ -1149,8 +1149,16 @@ int __init __weak early_init_dt_mark_hotplug_memory_arch(u64 base, u64 size) int __init __weak early_init_dt_reserve_memory_arch(phys_addr_t base, phys_addr_t size, bool nomap) { - if (nomap) + if (nomap) { + /* + * If the memory is already reserved (by another region), we + * should not allow it to be marked nomap. + */ + if (memblock_is_region_reserved(base, size)) + return -EBUSY; + return memblock_mark_nomap(base, size); + } return memblock_reserve(base, size); }