There are a couple of reasons that the set_memory() functions are
problematic when STRICT_KERNEL_RWX isn't enabled:
- The linear mapping is a different size and apply_to_page_range()
may modify a giant section, breaking everything
- patch_instruction() doesn't know to work around a page being marked
RO, and will subsequently crash
The latter can be replicated by building a kernel with the set_memory()
patches but with STRICT_KERNEL_RWX off and running ftracetest.
Reported-by: Jordan Niethe <jniet...@gmail.com>
Signed-off-by: Russell Currey <rus...@russell.cc>
---
v4: new
arch/powerpc/mm/pageattr.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/mm/pageattr.c b/arch/powerpc/mm/pageattr.c
index ee6b5e3b7604..ff111930cf5e 100644
--- a/arch/powerpc/mm/pageattr.c
+++ b/arch/powerpc/mm/pageattr.c
@@ -96,12 +96,17 @@ static int set_page_attr(pte_t *ptep, unsigned long addr,
void *data)
int set_memory_attr(unsigned long addr, int numpages, pgprot_t prot)
{
- unsigned long start = ALIGN_DOWN(addr, PAGE_SIZE);
- unsigned long sz = numpages * PAGE_SIZE;
+ unsigned long start, size;
+
+ if (!IS_ENABLED(CONFIG_STRICT_KERNEL_RWX))
+ return 0;
if (!numpages)
return 0;
- return apply_to_page_range(&init_mm, start, sz, set_page_attr,
+ start = ALIGN_DOWN(addr, PAGE_SIZE);
+ size = numpages * PAGE_SIZE;
+
+ return apply_to_page_range(&init_mm, start, size, set_page_attr,
(void *)pgprot_val(prot));
}
--
2.25.1
