[PATCH] of: fdt: do not reserve memory below MIN_MEMBLOCK_ADDR

[Patrick Wang <patrick.wang.shcn@gmail.com>]

Dt reserve memory without base checking, which will trigger an oops in
kmemleak when the base address is below MIN_MEMBLOCK_ADDR:

# echo scan > /sys/kernel/debug/kmemleak
[   54.888353] Unable to handle kernel paging request at virtual address ff5fffffffe00000
[   54.888932] Oops [#1]
[   54.889102] Modules linked in:
[   54.889326] CPU: 2 PID: 134 Comm: bash Not tainted 5.18.0-rc1-next-20220407 #33
[   54.889620] Hardware name: riscv-virtio,qemu (DT)
[   54.889901] epc : scan_block+0x74/0x15c
[   54.890215]  ra : scan_block+0x72/0x15c
[   54.890390] epc : ffffffff801e5806 ra : ffffffff801e5804 sp : ff200000104abc30
[   54.890607]  gp : ffffffff815cd4e8 tp : ff60000004cfa340 t0 : 0000000000000200
[   54.890835]  t1 : 00aaaaaac23954cc t2 : 00000000000003ff s0 : ff200000104abc90
[   54.891024]  s1 : ffffffff81b0ff28 a0 : 0000000000000000 a1 : ff5fffffffe01000
[   54.891201]  a2 : ffffffff81b0ff28 a3 : 0000000000000002 a4 : 0000000000000001
[   54.891377]  a5 : 0000000000000000 a6 : ff200000104abd7c a7 : 0000000000000005
[   54.891552]  s2 : ff5fffffffe00ff9 s3 : ffffffff815cd998 s4 : ffffffff815d0e90
[   54.891727]  s5 : ffffffff81b0ff28 s6 : 0000000000000020 s7 : ffffffff815d0eb0
[   54.891903]  s8 : ffffffffffffffff s9 : ff5fffffffe00000 s10: ff5fffffffe01000
[   54.892078]  s11: 0000000000000022 t3 : 00ffffffaa17db4c t4 : 000000000000000f
[   54.892271]  t5 : 0000000000000001 t6 : 0000000000000000
[   54.892408] status: 0000000000000100 badaddr: ff5fffffffe00000 cause: 000000000000000d
[   54.892643] [<ffffffff801e5a1c>] scan_gray_list+0x12e/0x1a6
[   54.892824] [<ffffffff801e5d3e>] kmemleak_scan+0x2aa/0x57e
[   54.892961] [<ffffffff801e633c>] kmemleak_write+0x32a/0x40c
[   54.893096] [<ffffffff803915ac>] full_proxy_write+0x56/0x82
[   54.893235] [<ffffffff801ef456>] vfs_write+0xa6/0x2a6
[   54.893362] [<ffffffff801ef880>] ksys_write+0x6c/0xe2
[   54.893487] [<ffffffff801ef918>] sys_write+0x22/0x2a
[   54.893609] [<ffffffff8000397c>] ret_from_syscall+0x0/0x2
[   54.894183] ---[ end trace 0000000000000000 ]---

Add base checking and ignore the range lower than MIN_MEMBLOCK_ADDR.

Signed-off-by: Patrick Wang <patrick.wang.shcn@gmail.com>
---
 drivers/of/fdt.c | 27 ++++++++++++++++++++-------
 1 file changed, 20 insertions(+), 7 deletions(-)

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index ec315b060..296c4ab8e 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -33,6 +33,13 @@
 
 #include "of_private.h"
 
+#ifndef MIN_MEMBLOCK_ADDR
+#define MIN_MEMBLOCK_ADDR	__pa(PAGE_OFFSET)
+#endif
+#ifndef MAX_MEMBLOCK_ADDR
+#define MAX_MEMBLOCK_ADDR	((phys_addr_t)~0)
+#endif
+
 /*
  * of_fdt_limit_memory - limit the number of regions in the /memory node
  * @limit: maximum entries
@@ -480,6 +487,19 @@ static u32 of_fdt_crc32;
 static int __init early_init_dt_reserve_memory_arch(phys_addr_t base,
 					phys_addr_t size, bool nomap)
 {
+	const u64 phys_offset = MIN_MEMBLOCK_ADDR;
+
+	if (base < phys_offset) {
+		pr_warn("Ignoring reserved memory range 0x%llx - 0x%llx\n",
+			base, phys_offset);
+		size = (phys_offset - base) < size ?
+			size - (phys_offset - base) : 0;
+		base = phys_offset;
+
+		if (!size)
+			return -EFAULT;
+	}
+
 	if (nomap) {
 		/*
 		 * If the memory is already reserved (by another region), we
@@ -1198,13 +1218,6 @@ int __init early_init_dt_scan_chosen(char *cmdline)
 	return 0;
 }
 
-#ifndef MIN_MEMBLOCK_ADDR
-#define MIN_MEMBLOCK_ADDR	__pa(PAGE_OFFSET)
-#endif
-#ifndef MAX_MEMBLOCK_ADDR
-#define MAX_MEMBLOCK_ADDR	((phys_addr_t)~0)
-#endif
-
 void __init __weak early_init_dt_add_memory_arch(u64 base, u64 size)
 {
 	const u64 phys_offset = MIN_MEMBLOCK_ADDR;
-- 
2.25.1