[PATCH 0/2 v2] core dump: re-purpose VM_ALWAYSDUMP to user controlled VM_NODUMP

The VM_ALWAYSDUMP flag is currently used by the coredump code to indicate that
a vma is part of a vsyscall or vdso section. However, we can determine if a vma
is in one these sections by checking it against the gate_vma and checking for a
non-NULL return value from arch_vma_name(). Thus, freeing a valuable vma bit.

Signed-off-by: Jason Baron

arch/arm/kernel/process.c | 2 +-
arch/hexagon/kernel/vdso.c | 3 +--
arch/mips/kernel/vdso.c | 3 +--
arch/powerpc/kernel/vdso.c | 10 ++--
arch/s390/kernel/vdso.c | 10 ++--
arch/sh/kernel/vsyscall/vsyscall.c | 3 +--
arch/tile/mm/elf.c | 8 +-
arch/unicore32/kernel/process.c | 2 +-
arch/x86/um/mem_32.c | 8 --
arch/x86/um/vdso/vma.c | 3 +--
arch/x86/vdso/vdso32-setup.c | 17 ++
arch/x86/vdso/vma.c | 3 +--
fs/binfmt_elf.c | 27 +++++++++++++++++++++++++--
include/linux/mm.h | 1 -
mm/memory.c | 8 +-
15 files changed, 40 insertions(+), 68 deletions(-)

diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index 971d65c..565ac89 100644
a/arch/arm/kernel/process.c
+++ b/arch/arm/kernel/process.c
@@ -536,7 +536,7 @@ int vectors_user_mapping(void)
return install_special_mapping(mm, 0xffff0000, PAGE_SIZE,
VM_READ | VM_EXEC |
VM_MAYREAD | VM_MAYEXEC |
- VM_ALWAYSDUMP | VM_RESERVED,
+ VM_RESERVED,
NULL);
}

diff --git a/arch/hexagon/kernel/vdso.c b/arch/hexagon/kernel/vdso.c
index 16277c3..f212a45 100644
a/arch/hexagon/kernel/vdso.c
+++ b/arch/hexagon/kernel/vdso.c
@@ -78,8 +78,7 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
/* MAYWRITE to allow gdb to COW and set breakpoints. */
ret = install_special_mapping(mm, vdso_base, PAGE_SIZE,
VM_READ|VM_EXEC|
- VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
- VM_ALWAYSDUMP,
+ VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
&vdso_page);

if (ret)
diff --git a/arch/mips/kernel/vdso.c b/arch/mips/kernel/vdso.c
index e5cdfd6..0f1af58 100644
a/arch/mips/kernel/vdso.c
+++ b/arch/mips/kernel/vdso.c
@@ -88,8 +88,7 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)

ret = install_special_mapping(mm, addr, PAGE_SIZE,
VM_READ|VM_EXEC|
- VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
- VM_ALWAYSDUMP,
+ VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
&vdso_page);

if (ret)
diff --git a/arch/powerpc/kernel/vdso.c b/arch/powerpc/kernel/vdso.c
index 7d14bb6..d36ee10 100644
a/arch/powerpc/kernel/vdso.c
+++ b/arch/powerpc/kernel/vdso.c
@@ -263,17 +263,11 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
* the "data" page of the vDSO or you'll stop getting kernel updates
* and your nice userland gettimeofday will be totally dead.
* It's fine to use that for setting breakpoints in the vDSO code
- * pages though
- *
- * Make sure the vDSO gets into every core dump.
- * Dumping its contents makes post-mortem fully interpretable later
- * without matching up the same kernel and hardware config to see
- * what PC values meant.
+ * pages though.
*/
rc = install_special_mapping(mm, vdso_base, vdso_pages << PAGE_SHIFT,
VM_READ|VM_EXEC|
- VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
- VM_ALWAYSDUMP,
+ VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
vdso_pagelist);
if (rc) {
current->mm->context.vdso_base = 0;
diff --git a/arch/s390/kernel/vdso.c b/arch/s390/kernel/vdso.c
index d73630b..904df23 100644
a/arch/s390/kernel/vdso.c
+++ b/arch/s390/kernel/vdso.c
@@ -253,17 +253,11 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
* on the "data" page of the vDSO or you'll stop getting kernel
* updates and your nice userland gettimeofday will be totally dead.
* It's fine to use that for setting breakpoints in the vDSO code
- * pages though
- *
- * Make sure the vDSO gets into every core dump.
- * Dumping its contents makes post-mortem fully interpretable later
- * without matching up the same kernel and hardware config to see
- * what PC values meant.
+ * pages though.
*/
rc = install_special_mapping(mm, vdso_base, vdso_pages << PAGE_SHIFT,
VM_READ|VM_EXEC|
- VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
- VM_ALWAYSDUMP,
+ VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
vdso_pagelist);
if (rc)
current->mm->context.vdso_base = 0;
diff --git a/arch/sh/kernel/vsyscall/vsyscall.c b/arch/sh/kernel/vsyscall/vsyscall.c
index 1d6d51a..5ca5797 100644
a/arch/sh/kernel/vsyscall/vsyscall.c
+++ b/arch/sh/kernel/vsyscall/vsyscall.c
@@ -73,8 +73,7 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)

ret = install_special_mapping(mm, addr, PAGE_SIZE,
VM_READ | VM_EXEC |
- VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC |
- VM_ALWAYSDUMP,
+ VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
syscall_pages);
if (unlikely(ret))
goto up_fail;
diff --git a/arch/tile/mm/elf.c b/arch/tile/mm/elf.c
index 55e58e9..1a00fb6 100644
a/arch/tile/mm/elf.c
+++ b/arch/tile/mm/elf.c
@@ -117,17 +117,11 @@ int arch_setup_additional_pages(struct linux_binprm *bprm,

/*
* MAYWRITE to allow gdb to COW and set breakpoints
- *
- * Make sure the vDSO gets into every core dump. Dumping its
- * contents makes post-mortem fully interpretable later
- * without matching up the same kernel and hardware config to
- * see what PC values meant.
*/
vdso_base = VDSO_BASE;
retval = install_special_mapping(mm, vdso_base, PAGE_SIZE,
VM_READ|VM_EXEC|
- VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
- VM_ALWAYSDUMP,
+ VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
vdso_pages);

#ifndef __tilegx__
diff --git a/arch/unicore32/kernel/process.c b/arch/unicore32/kernel/process.c
index 52edc2b..432b429 100644
a/arch/unicore32/kernel/process.c
+++ b/arch/unicore32/kernel/process.c
@@ -381,7 +381,7 @@ int vectors_user_mapping(void)
return install_special_mapping(mm, 0xffff0000, PAGE_SIZE,
VM_READ | VM_EXEC |
VM_MAYREAD | VM_MAYEXEC |
- VM_ALWAYSDUMP | VM_RESERVED,
+ VM_RESERVED,
NULL);
}

diff --git a/arch/x86/um/mem_32.c b/arch/x86/um/mem_32.c
index 639900a..f40281e 100644
a/arch/x86/um/mem_32.c
+++ b/arch/x86/um/mem_32.c
@@ -23,14 +23,6 @@ static int __init gate_vma_init(void)
gate_vma.vm_flags = VM_READ | VM_MAYREAD | VM_EXEC | VM_MAYEXEC;
gate_vma.vm_page_prot = __P101;

- /*
- * Make sure the vDSO gets into every core dump.
- * Dumping its contents makes post-mortem fully interpretable later
- * without matching up the same kernel and hardware config to see
- * what PC values meant.
- */
- gate_vma.vm_flags |= VM_ALWAYSDUMP;
-
return 0;
}
__initcall(gate_vma_init);
diff --git a/arch/x86/um/vdso/vma.c b/arch/x86/um/vdso/vma.c
index 91f4ec9..af91901 100644
a/arch/x86/um/vdso/vma.c
+++ b/arch/x86/um/vdso/vma.c
@@ -64,8 +64,7 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)

err = install_special_mapping(mm, um_vdso_addr, PAGE_SIZE,
VM_READ|VM_EXEC|
- VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
- VM_ALWAYSDUMP,
+ VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
vdsop);

up_write(&mm->mmap_sem);
diff --git a/arch/x86/vdso/vdso32-setup.c b/arch/x86/vdso/vdso32-setup.c
index 468d591..a944020 100644
a/arch/x86/vdso/vdso32-setup.c
+++ b/arch/x86/vdso/vdso32-setup.c
@@ -250,13 +250,7 @@ static int __init gate_vma_init(void)
gate_vma.vm_end = FIXADDR_USER_END;
gate_vma.vm_flags = VM_READ | VM_MAYREAD | VM_EXEC | VM_MAYEXEC;
gate_vma.vm_page_prot = __P101;
- /*
- * Make sure the vDSO gets into every core dump.
- * Dumping its contents makes post-mortem fully interpretable later
- * without matching up the same kernel and hardware config to see
- * what PC values meant.
- */
- gate_vma.vm_flags |= VM_ALWAYSDUMP;
+
return 0;
}

@@ -343,17 +337,10 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
if (compat_uses_vma || !compat) {
/*
* MAYWRITE to allow gdb to COW and set breakpoints
- *
- * Make sure the vDSO gets into every core dump.
- * Dumping its contents makes post-mortem fully
- * interpretable later without matching up the same
- * kernel and hardware config to see what PC values
- * meant.
*/
ret = install_special_mapping(mm, addr, PAGE_SIZE,
VM_READ|VM_EXEC|
- VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
- VM_ALWAYSDUMP,
+ VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
vdso32_pages);

if (ret)
diff --git a/arch/x86/vdso/vma.c b/arch/x86/vdso/vma.c
index 153407c..17e1827 100644
a/arch/x86/vdso/vma.c
+++ b/arch/x86/vdso/vma.c
@@ -124,8 +124,7 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)

ret = install_special_mapping(mm, addr, vdso_size,
VM_READ|VM_EXEC|
- VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
- VM_ALWAYSDUMP,
+ VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
vdso_pages);
if (ret) {
current->mm->context.vdso = NULL;
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 07d096c..93b7adb 100644
a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1095,6 +1095,29 @@ out:
*/

/*
+ * The purpose of always_dump_vma() is to make sure that special kernel mappings
+ * that are useful for post-mortem analysis are included in every core dump.
+ * In that way we ensure that the core dump is fully interpretable later
+ * without matching up the same kernel and hardware config to see what PC values
+ * meant. These special mappings include - vDSO, vsyscall, and other
+ * architecture specific mappings
+ */
+static bool always_dump_vma(struct vm_area_struct *vma)
+{
+ /* Any vsyscall mappings? */
+ if (vma == get_gate_vma(vma->vm_mm))
+ return true;
+ /*
+ * arch_vma_name() returns non-NULL for special architecture mappings,
+ * such as vDSO sections.
+ */
+ if (arch_vma_name(vma))
+ return true;
+
+ return false;
+}
+
+/*
* Decide what to dump of a segment, part, all or none.
*/
static unsigned long vma_dump_size(struct vm_area_struct *vma,
@@ -1102,8 +1125,8 @@ static unsigned long vma_dump_size(struct vm_area_struct *vma,
{
#define FILTER(type) (mm_flags & (1UL << MMF_DUMP_##type))

- /* The vma can be set up to tell us the answer directly. */
- if (vma->vm_flags & VM_ALWAYSDUMP)
+ /* always dump the vdso and vsyscall sections */
+ if (always_dump_vma(vma))
goto whole;

/* Hugetlb memory check */
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 17b27cd..a296709 100644
a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -111,7 +111,6 @@ extern unsigned int kobjsize(const void *objp);
#define VM_HUGEPAGE 0x01000000 /* MADV_HUGEPAGE marked this vma */
#endif
#define VM_INSERTPAGE 0x02000000 /* The vma has had "vm_insert_page()" done on it */
-#define VM_ALWAYSDUMP 0x04000000 /* Always include in core dumps */

#define VM_CAN_NONLINEAR 0x08000000 /* Has ->fault & does nonlinear pages */
#define VM_MIXEDMAP 0x10000000 /* Can contain "struct page" and pure PFN pages */
diff --git a/mm/memory.c b/mm/memory.c
index fa2f04e..9b55ab0 100644
a/mm/memory.c
+++ b/mm/memory.c
@@ -3611,13 +3611,7 @@ static int __init gate_vma_init(void)
gate_vma.vm_end = FIXADDR_USER_END;
gate_vma.vm_flags = VM_READ | VM_MAYREAD | VM_EXEC | VM_MAYEXEC;
gate_vma.vm_page_prot = __P101;
- /*
- * Make sure the vDSO gets into every core dump.
- * Dumping its contents makes post-mortem fully interpretable later
- * without matching up the same kernel and hardware config to see
- * what PC values meant.
- */
- gate_vma.vm_flags |= VM_ALWAYSDUMP;
+
return 0;
}
__initcall(gate_vma_init);
1.7.7.6

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