Commit d1befa65 authored by Vasily Gorbik's avatar Vasily Gorbik Committed by Martin Schwidefsky
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s390/vdso: avoid 64-bit vdso mapping for compat tasks 



vdso_fault used is_compat_task function (on s390 it tests "current"
thread_info flags) to distinguish compat tasks and map 31-bit vdso
pages. But "current" task might not correspond to mm context.

When 31-bit compat inferior is executed under gdb, gdb does
PTRACE_PEEKTEXT on vdso page, causing vdso_fault with "current" being
64-bit gdb process. So, 31-bit inferior ends up with 64-bit vdso mapped.

To avoid this problem a new compat_mm flag has been introduced into
mm context. This flag is used in vdso_fault and vdso_mremap instead
of is_compat_task.

Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent 1c472d46

arch/s390/include/asm/mmu.h

+2 −0
Original line number Diff line number Diff line
@@ -32,6 +32,8 @@ typedef struct { 
	unsigned int uses_cmm:1;

	/* The gmaps associated with this context are allowed to use huge pages. */

	unsigned int allow_gmap_hpage_1m:1;

	/* The mmu context is for compat task */

	unsigned int compat_mm:1;

} mm_context_t;



#define INIT_MM_CONTEXT(name)						   \

arch/s390/include/asm/mmu_context.h

+1 −0
Original line number Diff line number Diff line
@@ -25,6 +25,7 @@ static inline int init_new_context(struct task_struct *tsk, 
	atomic_set(&mm->context.flush_count, 0);

	mm->context.gmap_asce = 0;

	mm->context.flush_mm = 0;

	mm->context.compat_mm = 0;

#ifdef CONFIG_PGSTE

	mm->context.alloc_pgste = page_table_allocate_pgste ||

		test_thread_flag(TIF_PGSTE) ||

arch/s390/kernel/vdso.c

+5 −3
Original line number Diff line number Diff line
@@ -56,7 +56,7 @@ static vm_fault_t vdso_fault(const struct vm_special_mapping *sm, 
	vdso_pagelist = vdso64_pagelist;

	vdso_pages = vdso64_pages;

#ifdef CONFIG_COMPAT

	if (is_compat_task()) {

	if (vma->vm_mm->context.compat_mm) {

		vdso_pagelist = vdso32_pagelist;

		vdso_pages = vdso32_pages;

	}
@@ -77,7 +77,7 @@ static int vdso_mremap(const struct vm_special_mapping *sm, 


	vdso_pages = vdso64_pages;

#ifdef CONFIG_COMPAT

	if (is_compat_task())

	if (vma->vm_mm->context.compat_mm)

		vdso_pages = vdso32_pages;

#endif
@@ -224,8 +224,10 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) 


	vdso_pages = vdso64_pages;

#ifdef CONFIG_COMPAT

	if (is_compat_task())

	if (is_compat_task()) {

		vdso_pages = vdso32_pages;

		mm->context.compat_mm = 1;

	}

#endif

	/*

	 * vDSO has a problem and was disabled, just don't "enable" it for

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