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SubjectRe: "arm64/for-next/core" causes boot panic
[+Steve]

On Tue, Aug 13, 2019 at 11:58:52AM +0100, Will Deacon wrote:
> On Tue, Aug 13, 2019 at 10:02:01AM +0100, Will Deacon wrote:
> > On Mon, Aug 12, 2019 at 05:51:35PM -0400, Qian Cai wrote:
> > > Booting today's linux-next on an arm64 server triggers a panic with
> > > CONFIG_KASAN_SW_TAGS=y pointing to this line,
> >
> > Is this the only change on top of defconfig? If not, please can you share
> > your full .config?
> >
> > > kfree()->virt_to_head_page()->compound_head()
> > >
> > > unsigned long head = READ_ONCE(page->compound_head);
> > >
> > > The bisect so far indicates one of those could be bad,
> >
> > I guess that means the issue is reproducible on the arm64 for-next/core
> > branch. Once I have your .config, I'll give it a go.
>
> FWIW, I've managed to reproduce this using defconfig + SW_TAGS on
> for-next/core, so I'll keep investigating.

Right, hacky diff below seems to resolve this, so I'll split this up into
some proper patches as there is more than one bug here.

Thanks,

Will

--->8

diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index afaf512c0e1b..541e8dcb5ab3 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -244,7 +244,7 @@ static inline const void *__tag_set(const void *addr, u8 tag)
/*
* The linear kernel range starts in the middle of the virtual adddress
* space. Testing the top bit for the start of the region is a
- * sufficient check.
+ * sufficient check and avoids having to worry about the tag.
*/
#define __is_lm_address(addr) (!((addr) & BIT(vabits_actual - 1)))

@@ -252,7 +252,7 @@ static inline const void *__tag_set(const void *addr, u8 tag)
#define __kimg_to_phys(addr) ((addr) - kimage_voffset)

#define __virt_to_phys_nodebug(x) ({ \
- phys_addr_t __x = (phys_addr_t)(x); \
+ phys_addr_t __x = (phys_addr_t)(__tag_reset(x)); \
__is_lm_address(__x) ? __lm_to_phys(__x) : \
__kimg_to_phys(__x); \
})
@@ -301,8 +301,8 @@ static inline void *phys_to_virt(phys_addr_t x)
#define __pa_nodebug(x) __virt_to_phys_nodebug((unsigned long)(x))
#define __va(x) ((void *)__phys_to_virt((phys_addr_t)(x)))
#define pfn_to_kaddr(pfn) __va((pfn) << PAGE_SHIFT)
-#define virt_to_pfn(x) __phys_to_pfn(__virt_to_phys((unsigned long)(x)))
-#define sym_to_pfn(x) __phys_to_pfn(__pa_symbol(x))
+#define virt_to_pfn(x) __phys_to_pfn(__virt_to_phys((unsigned long)(x)))
+#define sym_to_pfn(x) __phys_to_pfn(__pa_symbol(x))

/*
* virt_to_page(k) convert a _valid_ virtual address to struct page *
@@ -311,7 +311,7 @@ static inline void *phys_to_virt(phys_addr_t x)
#define ARCH_PFN_OFFSET ((unsigned long)PHYS_PFN_OFFSET)

#if !defined(CONFIG_SPARSEMEM_VMEMMAP) || defined(CONFIG_DEBUG_VIRTUAL)
-#define virt_to_page(kaddr) pfn_to_page(__pa(kaddr) >> PAGE_SHIFT)
+#define virt_to_page(kaddr) pfn_to_page(virt_to_pfn(kaddr))
#else
#define __virt_to_pgoff(kaddr) (((u64)(kaddr) - PAGE_OFFSET) / PAGE_SIZE * sizeof(struct page))
#define __page_to_voff(kaddr) (((u64)(kaddr) - VMEMMAP_START) * PAGE_SIZE / sizeof(struct page))
@@ -324,15 +324,17 @@ static inline void *phys_to_virt(phys_addr_t x)
((void *)__addr_tag); \
})

-#define virt_to_page(vaddr) ((struct page *)((__virt_to_pgoff(vaddr)) + VMEMMAP_START))
+#define virt_to_page(kaddr) ({ \
+ unsigned long __addr = __tag_reset((unsigned long)kaddr); \
+ (struct page *)((__virt_to_pgoff(__addr) + VMEMMAP_START)); \
+})
#endif
#endif

-#define _virt_addr_is_linear(kaddr) \
- (__tag_reset((u64)(kaddr)) >= PAGE_OFFSET)
-
-#define virt_addr_valid(kaddr) \
- (_virt_addr_is_linear(kaddr) && pfn_valid(virt_to_pfn(kaddr)))
+#define virt_addr_valid(kaddr) ({ \
+ unsigned long __addr = (unsigned long)kaddr; \
+ __is_lm_address(__addr) && pfn_valid(virt_to_pfn(__addr)); \
+})

/*
* Given that the GIC architecture permits ITS implementations that can only be
\
 
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