185 lines
6.0 KiB
Diff
185 lines
6.0 KiB
Diff
From: Nick Piggin <npiggin@novell.com>
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Subject: Add mark_rodata_rw() to un-protect read-only kernel code pages
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References: bnc#439348
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Patch-mainline: probably never
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CONFIG_RODATA presents a problem for antivirus vendors who do not have a
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clean user-space interface for getting virus scanning triggered, and
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currently resort to patching the kernel code instead (presumably the
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ystem call table). With CONFIG_RODATA enabled, the kernel rejects such
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write accesses.
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Add a new mark_rodata_rw() function to un-protect the read-only kernel code
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pages for now, and export mark_rodata_ro() and mark_rodata_rw() to modules.
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This is not meant as a permanent workaround, and will be removed again in the
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next release!
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Acked-by: Andres Gruenbacher <agruen@suse.de>
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---
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arch/x86/include/asm/cacheflush.h | 3 +++
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arch/x86/mm/init_32.c | 14 ++++++++++++++
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arch/x86/mm/init_64.c | 31 +++++++++++++++++++++++++------
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arch/x86/mm/pageattr.c | 30 ++++++++++++++++++++++++++++--
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4 files changed, 70 insertions(+), 8 deletions(-)
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--- a/arch/x86/include/asm/cacheflush.h
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+++ b/arch/x86/include/asm/cacheflush.h
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@@ -135,6 +135,7 @@ int set_memory_x(unsigned long addr, int
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int set_memory_nx(unsigned long addr, int numpages);
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int set_memory_ro(unsigned long addr, int numpages);
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int set_memory_rw(unsigned long addr, int numpages);
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+int set_memory_rw_force(unsigned long addr, int numpages);
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int set_memory_np(unsigned long addr, int numpages);
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int set_memory_4k(unsigned long addr, int numpages);
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@@ -170,12 +171,14 @@ int set_pages_x(struct page *page, int n
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int set_pages_nx(struct page *page, int numpages);
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int set_pages_ro(struct page *page, int numpages);
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int set_pages_rw(struct page *page, int numpages);
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+int set_pages_rw_force(struct page *page, int numpages);
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void clflush_cache_range(void *addr, unsigned int size);
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#ifdef CONFIG_DEBUG_RODATA
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void mark_rodata_ro(void);
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+void mark_rodata_rw(void);
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extern const int rodata_test_data;
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extern int kernel_set_to_readonly;
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void set_kernel_text_rw(void);
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--- a/arch/x86/mm/init_32.c
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+++ b/arch/x86/mm/init_32.c
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@@ -1068,6 +1068,20 @@ void mark_rodata_ro(void)
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set_pages_ro(virt_to_page(start), size >> PAGE_SHIFT);
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#endif
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}
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+EXPORT_SYMBOL_GPL(mark_rodata_ro);
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+
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+void mark_rodata_rw(void)
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+{
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+ unsigned long start = PFN_ALIGN(_text);
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+ unsigned long size = PFN_ALIGN(_etext) - start;
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+
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+ start += size;
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+ size = (unsigned long)__end_rodata - start;
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+ set_pages_rw_force(virt_to_page(start), size >> PAGE_SHIFT);
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+ printk(KERN_INFO "Write enabling the kernel read-only data: %luk\n",
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+ size >> 10);
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+}
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+EXPORT_SYMBOL_GPL(mark_rodata_rw);
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#endif
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int __init reserve_bootmem_generic(unsigned long phys, unsigned long len,
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--- a/arch/x86/mm/init_64.c
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+++ b/arch/x86/mm/init_64.c
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@@ -755,6 +755,7 @@ void set_kernel_text_ro(void)
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set_memory_ro(start, (end - start) >> PAGE_SHIFT);
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}
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+static int initmem_freed __read_mostly = 0;
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void mark_rodata_ro(void)
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{
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unsigned long start = PFN_ALIGN(_text);
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@@ -787,15 +788,33 @@ void mark_rodata_ro(void)
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set_memory_ro(start, (end-start) >> PAGE_SHIFT);
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#endif
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- free_init_pages("unused kernel memory",
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- (unsigned long) page_address(virt_to_page(text_end)),
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- (unsigned long)
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+ if (!initmem_freed) {
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+ initmem_freed = 1;
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+ free_init_pages("unused kernel memory",
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+ (unsigned long)
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+ page_address(virt_to_page(text_end)),
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+ (unsigned long)
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page_address(virt_to_page(rodata_start)));
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- free_init_pages("unused kernel memory",
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- (unsigned long) page_address(virt_to_page(rodata_end)),
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- (unsigned long) page_address(virt_to_page(data_start)));
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+ free_init_pages("unused kernel memory",
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+ (unsigned long)
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+ page_address(virt_to_page(rodata_end)),
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+ (unsigned long)
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+ page_address(virt_to_page(data_start)));
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+ }
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}
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+EXPORT_SYMBOL_GPL(mark_rodata_ro);
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+void mark_rodata_rw(void)
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+{
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+ unsigned long rodata_start =
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+ ((unsigned long)__start_rodata + PAGE_SIZE - 1) & PAGE_MASK;
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+ unsigned long end = (unsigned long) &__end_rodata_hpage_align;
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+
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+ printk(KERN_INFO "Write protecting the kernel read-only data: %luk\n",
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+ (end - rodata_start) >> 10);
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+ set_memory_rw_force(rodata_start, (end - rodata_start) >> PAGE_SHIFT);
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+}
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+EXPORT_SYMBOL_GPL(mark_rodata_rw);
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#endif
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int __init reserve_bootmem_generic(unsigned long phys, unsigned long len,
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--- a/arch/x86/mm/pageattr.c
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+++ b/arch/x86/mm/pageattr.c
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@@ -245,6 +245,8 @@ static void cpa_flush_array(unsigned lon
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}
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}
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+static int static_protections_allow_rodata __read_mostly;
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+
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/*
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* Certain areas of memory on x86 require very specific protection flags,
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* for example the BIOS area or kernel text. Callers don't always get this
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@@ -276,8 +278,10 @@ static inline pgprot_t static_protection
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* catches all aliases.
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*/
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if (within(pfn, __pa((unsigned long)__start_rodata) >> PAGE_SHIFT,
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- __pa((unsigned long)__end_rodata) >> PAGE_SHIFT))
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- pgprot_val(forbidden) |= _PAGE_RW;
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+ __pa((unsigned long)__end_rodata) >> PAGE_SHIFT)) {
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+ if (!static_protections_allow_rodata)
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+ pgprot_val(forbidden) |= _PAGE_RW;
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+ }
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#if defined(CONFIG_X86_64) && defined(CONFIG_DEBUG_RODATA)
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/*
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@@ -1134,6 +1138,21 @@ int set_memory_rw(unsigned long addr, in
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}
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EXPORT_SYMBOL_GPL(set_memory_rw);
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+/* hack: bypass kernel rodata section static_protections check. */
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+int set_memory_rw_force(unsigned long addr, int numpages)
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+{
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+ static DEFINE_MUTEX(lock);
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+ int ret;
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+
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+ mutex_lock(&lock);
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+ static_protections_allow_rodata = 1;
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+ ret = change_page_attr_set(&addr, numpages, __pgprot(_PAGE_RW), 0);
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+ static_protections_allow_rodata = 0;
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+ mutex_unlock(&lock);
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+
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+ return ret;
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+}
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+
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int set_memory_np(unsigned long addr, int numpages)
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{
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return change_page_attr_clear(&addr, numpages, __pgprot(_PAGE_PRESENT), 0);
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@@ -1248,6 +1267,13 @@ int set_pages_rw(struct page *page, int
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return set_memory_rw(addr, numpages);
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}
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+int set_pages_rw_force(struct page *page, int numpages)
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+{
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+ unsigned long addr = (unsigned long)page_address(page);
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+
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+ return set_memory_rw_force(addr, numpages);
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+}
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+
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#ifdef CONFIG_DEBUG_PAGEALLOC
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static int __set_pages_p(struct page *page, int numpages)
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