On 11/4/25 6:02 AM, Dev Jain wrote:

On 04/11/25 1:15 am, Yang Shi wrote:

quoted

Since commit a166563e7ec3 ("arm64: mm: support large block mapping when
rodata=full"), __change_memory_common has more chance to fail due to
memory allocation fialure when splitting page table. So check the return
value of set_memory_rox(), then bail out if it fails otherwise we may 
have
RW memory mapping for kprobes insn page.

Fixes: 195a1b7d8388 ("arm64: kprobes: call set_memory_rox() for 
kprobe page")
Signed-off-by: Yang Shi <redacted>
---
I actually epxected 195a1b7d8388 ("arm64: kprobes: call set_memory_rox()
for kprobe page") can be merged in 6.17-rcX, so I just restored it to
before commit 10d5e97c1bf8 ("arm64: use PAGE_KERNEL_ROX directly in
alloc_insn_page"), however it turned out to be merged in 6.18-rc1 and it
is after commit a166563e7ec3 ("arm64: mm: support large block mapping 
when
rodata=full"). So I made the fix tag point to it.
And I don't think we need to backport this patch to pre-6.18.

  arch/arm64/kernel/probes/kprobes.c | 5 ++++-
  1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/probes/kprobes.c 

b/arch/arm64/kernel/probes/kprobes.c
index 8ab6104a4883..43a0361a8bf0 100644

--- a/arch/arm64/kernel/probes/kprobes.c
+++ b/arch/arm64/kernel/probes/kprobes.c

@@ -49,7 +49,10 @@ void *alloc_insn_page(void)

      addr = execmem_alloc(EXECMEM_KPROBES, PAGE_SIZE);
      if (!addr)
          return NULL;
-    set_memory_rox((unsigned long)addr, 1);
+    if (set_memory_rox((unsigned long)addr, 1)) {
+        execmem_free(addr);
+        return NULL;
+    }
      return addr;
  }

Looks obviously correct:

Reviewed-by: Dev Jain <dev.jain@arm.com>

Thank you.

Although I got confused by why set_memory_rox() is being called; it is 
being used
only to handle the linear map alias perm change, which is not nice :) 
but I don't
see an obvious way to refactor the code to only perform the needed 
functionality here,
and probably this is not a hot path that we care about.

Catalin actually raised the similar suggestion before. He suggested 
extract the linear mapping update code into a helper then just call it 
here if I remember correctly. However I have not gotten time to look it 
deeper yet. Anyway we agree it is not a critical path. It may be not 
worth all the effort.

Thanks,
Yang