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Date: Wed, 26 Feb 2020 17:35:51 +1100
From: Russell Currey <ruscur@...sell.cc>
To: linuxppc-dev@...ts.ozlabs.org
Cc: jniethe5@...il.com,
Russell Currey <ruscur@...sell.cc>,
christophe.leroy@....fr,
joel@....id.au,
mpe@...erman.id.au,
ajd@...ux.ibm.com,
dja@...ens.net,
npiggin@...il.com,
kernel-hardening@...ts.openwall.com
Subject: [PATCH v5 8/8] powerpc/mm: Disable set_memory() routines when strict RWX isn't enabled
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 <jniethe5@...il.com>
Signed-off-by: Russell Currey <ruscur@...sell.cc>
---
v5: Apply to both set_memory_attr() and change_memory_attr()
v4: New
arch/powerpc/mm/pageattr.c | 22 ++++++++++++++++------
1 file changed, 16 insertions(+), 6 deletions(-)
diff --git a/arch/powerpc/mm/pageattr.c b/arch/powerpc/mm/pageattr.c
index ee6b5e3b7604..49b8e2e0581d 100644
--- a/arch/powerpc/mm/pageattr.c
+++ b/arch/powerpc/mm/pageattr.c
@@ -64,13 +64,18 @@ static int change_page_attr(pte_t *ptep, unsigned long addr, void *data)
int change_memory_attr(unsigned long addr, int numpages, long action)
{
- 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, change_page_attr, (void *)action);
+ start = ALIGN_DOWN(addr, PAGE_SIZE);
+ size = numpages * PAGE_SIZE;
+
+ return apply_to_page_range(&init_mm, start, size, change_page_attr, (void *)action);
}
/*
@@ -96,12 +101,17 @@ 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
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