diff options
| author | Frank Rowand <frank.rowand@am.sony.com> | 2011-10-02 01:58:13 (GMT) |
|---|---|---|
| committer | Scott Wood <scottwood@freescale.com> | 2014-05-14 18:38:04 (GMT) |
| commit | e140bfa3a880aba70d6e04b54ae80805de86e41e (patch) | |
| tree | e2e2d9e8a290bd6554aacab218cbb3a98d1b9d55 /arch/arm | |
| parent | a210d5b3fe0a4efdf5b7f40b6f111e7c621c1f92 (diff) | |
| download | linux-fsl-qoriq-e140bfa3a880aba70d6e04b54ae80805de86e41e.tar.xz | |
ARM: Initialize ptl->lock for vector page
Without this patch, ARM can not use SPLIT_PTLOCK_CPUS if
PREEMPT_RT_FULL=y because vectors_user_mapping() creates a
VM_ALWAYSDUMP mapping of the vector page (address 0xffff0000), but no
ptl->lock has been allocated for the page. An attempt to coredump
that page will result in a kernel NULL pointer dereference when
follow_page() attempts to lock the page.
The call tree to the NULL pointer dereference is:
do_notify_resume()
get_signal_to_deliver()
do_coredump()
elf_core_dump()
get_dump_page()
__get_user_pages()
follow_page()
pte_offset_map_lock() <----- a #define
...
rt_spin_lock()
The underlying problem is exposed by mm-shrink-the-page-frame-to-rt-size.patch.
Signed-off-by: Frank Rowand <frank.rowand@am.sony.com>
Cc: Frank <Frank_Rowand@sonyusa.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/4E87C535.2030907@am.sony.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'arch/arm')
| -rw-r--r-- | arch/arm/kernel/process.c | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c index 92f7b15..83af229 100644 --- a/arch/arm/kernel/process.c +++ b/arch/arm/kernel/process.c @@ -432,6 +432,30 @@ unsigned long arch_randomize_brk(struct mm_struct *mm) } #ifdef CONFIG_MMU +/* + * CONFIG_SPLIT_PTLOCK_CPUS results in a page->ptl lock. If the lock is not + * initialized by pgtable_page_ctor() then a coredump of the vector page will + * fail. + */ +static int __init vectors_user_mapping_init_page(void) +{ + struct page *page; + unsigned long addr = 0xffff0000; + pgd_t *pgd; + pud_t *pud; + pmd_t *pmd; + + pgd = pgd_offset_k(addr); + pud = pud_offset(pgd, addr); + pmd = pmd_offset(pud, addr); + page = pmd_page(*(pmd)); + + pgtable_page_ctor(page); + + return 0; +} +late_initcall(vectors_user_mapping_init_page); + #ifdef CONFIG_KUSER_HELPERS /* * The vectors page is always readable from user space for the |