diff options
Diffstat (limited to 'debian/patches-rt/0080-ARM-Initialize-split-page-table-locks-for-vector-pag.patch')
| -rw-r--r-- | debian/patches-rt/0080-ARM-Initialize-split-page-table-locks-for-vector-pag.patch | 76 |
1 files changed, 76 insertions, 0 deletions
diff --git a/debian/patches-rt/0080-ARM-Initialize-split-page-table-locks-for-vector-pag.patch b/debian/patches-rt/0080-ARM-Initialize-split-page-table-locks-for-vector-pag.patch new file mode 100644 index 000000000..d983a6470 --- /dev/null +++ b/debian/patches-rt/0080-ARM-Initialize-split-page-table-locks-for-vector-pag.patch @@ -0,0 +1,76 @@ +From 2056bb928af7ba7036b8d058c0a52a182cd0b9b6 Mon Sep 17 00:00:00 2001 +From: Frank Rowand <frank.rowand@am.sony.com> +Date: Sat, 1 Oct 2011 18:58:13 -0700 +Subject: [PATCH 080/347] ARM: Initialize split page table locks for vector + page +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.246-rt110.tar.xz + +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> +--- + arch/arm/kernel/process.c | 24 ++++++++++++++++++++++++ + 1 file changed, 24 insertions(+) + +diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c +index 82ab015bf42b..8d3c7ce34c24 100644 +--- a/arch/arm/kernel/process.c ++++ b/arch/arm/kernel/process.c +@@ -324,6 +324,30 @@ 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 +-- +2.36.1 + |