Re: [PATCH v4 3/3] riscv: kdump: Fix crash memory reserve exceed system memory bug

On Mon, Jul 22, 2024 at 03:08:29PM +0800, Jinjie Ruan wrote:

quoted

On 2024/7/22 14:38, Mike Rapoport wrote:

quoted

Hi,

On Mon, Jul 22, 2024 at 11:57:01AM +0800, Jinjie Ruan wrote:

quoted

Similar with x86_32, on Riscv32 Qemu "virt" machine with 1GB memory, the
crash kernel "crashkernel=4G" is ok as below:
	crashkernel reserved: 0x00000000bf400000 - 0x00000001bf400000 (4096 MB)

The cause is that the crash_size is parsed and printed with "unsigned long
long" data type which is 8 bytes but allocated used with "phys_addr_t"
which is 4 bytes in memblock_phys_alloc_range().

Fix it by checking if the crash_size is greater than system RAM size and
warn out as parse_crashkernel_mem() do it if so.

After this patch, it fails and there is no above confusing reserve
success info.

Signed-off-by: Jinjie Ruan <redacted>
---
 arch/riscv/mm/init.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index bfa2dea95354..5d66a4937fcd 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c

@@ -1381,6 +1381,11 @@ static void __init arch_reserve_crashkernel(void)
 	if (ret)
 		return;
 
+	if (crash_size >= memblock_phys_mem_size()) {
+		pr_warn("Crashkernel: invalid size.");
+		return;
+	}
+

What the point of adding three identical checks right after the call to
parse_crashkernel()?

This check should be there and parse_crashkernel() should return error in
this case.

Hi, Mike

How about the folling rough patch?

--- a/kernel/crash_reserve.c
+++ b/kernel/crash_reserve.c

@@ -313,7 +313,7 @@ int __init parse_crashkernel(char *cmdline,
        if (high && ret == -ENOENT) {
                ret = __parse_crashkernel(cmdline, 0, crash_size,
                                crash_base, suffix_tbl[SUFFIX_HIGH]);
-               if (ret || !*crash_size)
+               if (ret || !*crash_size || crash_size >= system_ram)
                        return -EINVAL;

                /*

@@ -332,7 +332,7 @@ int __init parse_crashkernel(char *cmdline,
                *high = true;
        }
 #endif
-       if (!*crash_size)
+       if (!*crash_size || crash_size >= system_ram)
                ret = -EINVAL;

Why no simply

diff --git a/kernel/crash_reserve.c b/kernel/crash_reserve.c
index 5b2722a93a48..64312709877d 100644
--- a/kernel/crash_reserve.c
+++ b/kernel/crash_reserve.c

@@ -336,6 +336,9 @@ int __init parse_crashkernel(char *cmdline,
 	if (!*crash_size)
 		ret = -EINVAL;
 
+	if (*crash_size >= system_ram)
+		ret = -EINVAL;
+
 	return ret;