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authorJann Horn <jannh@google.com>2020-10-15 20:12:50 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-10-16 11:11:21 -0700
commit429a22e776a2b9f85a2b9c53d8e647598b553dd1 (patch)
tree152b8792f52db94707885477da6bb8d6e404de13 /fs/binfmt_elf.c
parentafc63a97b764bc5a715762d0d9cc9785c2ef4e75 (diff)
downloadlinux-429a22e776a2b9f85a2b9c53d8e647598b553dd1.tar.bz2
coredump: rework elf/elf_fdpic vma_dump_size() into common helper
At the moment, the binfmt_elf and binfmt_elf_fdpic code have slightly different code to figure out which VMAs should be dumped, and if so, whether the dump should contain the entire VMA or just its first page. Eliminate duplicate code by reworking the binfmt_elf version into a generic core dumping helper in coredump.c. As part of that, change the heuristic for detecting executable/library header pages to check whether the inode is executable instead of looking at the file mode. This is less problematic in terms of locking because it lets us avoid get_user() under the mmap_sem. (And arguably it looks nicer and makes more sense in generic code.) Adjust a little bit based on the binfmt_elf_fdpic version: ->anon_vma is only meaningful under CONFIG_MMU, otherwise we have to assume that the VMA has been written to. Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Jann Horn <jannh@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Christoph Hellwig <hch@lst.de> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: "Eric W . Biederman" <ebiederm@xmission.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Hugh Dickins <hughd@google.com> Link: http://lkml.kernel.org/r/20200827114932.3572699-5-jannh@google.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/binfmt_elf.c')
-rw-r--r--fs/binfmt_elf.c120
1 files changed, 0 insertions, 120 deletions
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index cf956edf05ef..c1756fd8d10b 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1414,126 +1414,6 @@ out:
* Jeremy Fitzhardinge <jeremy@sw.oz.au>
*/
-/*
- * 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;
-
- /*
- * Assume that all vmas with a .name op should always be dumped.
- * If this changes, a new vm_ops field can easily be added.
- */
- if (vma->vm_ops && vma->vm_ops->name && vma->vm_ops->name(vma))
- 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,
- unsigned long mm_flags)
-{
-#define FILTER(type) (mm_flags & (1UL << MMF_DUMP_##type))
-
- /* always dump the vdso and vsyscall sections */
- if (always_dump_vma(vma))
- goto whole;
-
- if (vma->vm_flags & VM_DONTDUMP)
- return 0;
-
- /* support for DAX */
- if (vma_is_dax(vma)) {
- if ((vma->vm_flags & VM_SHARED) && FILTER(DAX_SHARED))
- goto whole;
- if (!(vma->vm_flags & VM_SHARED) && FILTER(DAX_PRIVATE))
- goto whole;
- return 0;
- }
-
- /* Hugetlb memory check */
- if (is_vm_hugetlb_page(vma)) {
- if ((vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_SHARED))
- goto whole;
- if (!(vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_PRIVATE))
- goto whole;
- return 0;
- }
-
- /* Do not dump I/O mapped devices or special mappings */
- if (vma->vm_flags & VM_IO)
- return 0;
-
- /* By default, dump shared memory if mapped from an anonymous file. */
- if (vma->vm_flags & VM_SHARED) {
- if (file_inode(vma->vm_file)->i_nlink == 0 ?
- FILTER(ANON_SHARED) : FILTER(MAPPED_SHARED))
- goto whole;
- return 0;
- }
-
- /* Dump segments that have been written to. */
- if (vma->anon_vma && FILTER(ANON_PRIVATE))
- goto whole;
- if (vma->vm_file == NULL)
- return 0;
-
- if (FILTER(MAPPED_PRIVATE))
- goto whole;
-
- /*
- * If this looks like the beginning of a DSO or executable mapping,
- * check for an ELF header. If we find one, dump the first page to
- * aid in determining what was mapped here.
- */
- if (FILTER(ELF_HEADERS) &&
- vma->vm_pgoff == 0 && (vma->vm_flags & VM_READ)) {
- u32 __user *header = (u32 __user *) vma->vm_start;
- u32 word;
- /*
- * Doing it this way gets the constant folded by GCC.
- */
- union {
- u32 cmp;
- char elfmag[SELFMAG];
- } magic;
- BUILD_BUG_ON(SELFMAG != sizeof word);
- magic.elfmag[EI_MAG0] = ELFMAG0;
- magic.elfmag[EI_MAG1] = ELFMAG1;
- magic.elfmag[EI_MAG2] = ELFMAG2;
- magic.elfmag[EI_MAG3] = ELFMAG3;
- if (unlikely(get_user(word, header)))
- word = 0;
- if (word == magic.cmp)
- return PAGE_SIZE;
- }
-
-#undef FILTER
-
- return 0;
-
-whole:
- return vma->vm_end - vma->vm_start;
-}
-
/* An ELF note in memory */
struct memelfnote
{