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coredump: Use the vma snapshot in fill_files_note
Matthew Wilcox reported that there is a missing mmap_lock in file_files_note that could possibly lead to a user after free. Solve this by using the existing vma snapshot for consistency and to avoid the need to take the mmap_lock anywhere in the coredump code except for dump_vma_snapshot. Update the dump_vma_snapshot to capture vm_pgoff and vm_file that are neeeded by fill_files_note. Add free_vma_snapshot to free the captured values of vm_file. Reported-by: Matthew Wilcox <willy@infradead.org> Link: https://lkml.kernel.org/r/20220131153740.2396974-1-willy@infradead.org Cc: stable@vger.kernel.org Fixes:a07279c9a8
("binfmt_elf, binfmt_elf_fdpic: use a VMA list snapshot") Fixes:2aa362c49c
("coredump: extend core dump note section to contain file names of mapped files") Reviewed-by: Kees Cook <keescook@chromium.org> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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@ -1641,17 +1641,16 @@ static void fill_siginfo_note(struct memelfnote *note, user_siginfo_t *csigdata,
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* long file_ofs
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* followed by COUNT filenames in ASCII: "FILE1" NUL "FILE2" NUL...
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*/
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static int fill_files_note(struct memelfnote *note)
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static int fill_files_note(struct memelfnote *note, struct coredump_params *cprm)
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{
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struct mm_struct *mm = current->mm;
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struct vm_area_struct *vma;
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unsigned count, size, names_ofs, remaining, n;
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user_long_t *data;
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user_long_t *start_end_ofs;
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char *name_base, *name_curpos;
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int i;
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/* *Estimated* file count and total data size needed */
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count = mm->map_count;
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count = cprm->vma_count;
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if (count > UINT_MAX / 64)
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return -EINVAL;
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size = count * 64;
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@ -1673,11 +1672,12 @@ static int fill_files_note(struct memelfnote *note)
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name_base = name_curpos = ((char *)data) + names_ofs;
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remaining = size - names_ofs;
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count = 0;
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for (vma = mm->mmap; vma != NULL; vma = vma->vm_next) {
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for (i = 0; i < cprm->vma_count; i++) {
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struct core_vma_metadata *m = &cprm->vma_meta[i];
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struct file *file;
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const char *filename;
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file = vma->vm_file;
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file = m->file;
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if (!file)
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continue;
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filename = file_path(file, name_curpos, remaining);
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@ -1697,9 +1697,9 @@ static int fill_files_note(struct memelfnote *note)
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memmove(name_curpos, filename, n);
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name_curpos += n;
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*start_end_ofs++ = vma->vm_start;
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*start_end_ofs++ = vma->vm_end;
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*start_end_ofs++ = vma->vm_pgoff;
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*start_end_ofs++ = m->start;
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*start_end_ofs++ = m->end;
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*start_end_ofs++ = m->pgoff;
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count++;
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}
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@ -1710,7 +1710,7 @@ static int fill_files_note(struct memelfnote *note)
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* Count usually is less than mm->map_count,
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* we need to move filenames down.
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*/
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n = mm->map_count - count;
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n = cprm->vma_count - count;
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if (n != 0) {
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unsigned shift_bytes = n * 3 * sizeof(data[0]);
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memmove(name_base - shift_bytes, name_base,
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@ -1909,7 +1909,7 @@ static int fill_note_info(struct elfhdr *elf, int phdrs,
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fill_auxv_note(&info->auxv, current->mm);
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info->size += notesize(&info->auxv);
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if (fill_files_note(&info->files) == 0)
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if (fill_files_note(&info->files, cprm) == 0)
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info->size += notesize(&info->files);
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return 1;
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@ -2098,7 +2098,7 @@ static int fill_note_info(struct elfhdr *elf, int phdrs,
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fill_auxv_note(info->notes + 3, current->mm);
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info->numnote = 4;
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if (fill_files_note(info->notes + info->numnote) == 0) {
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if (fill_files_note(info->notes + info->numnote, cprm) == 0) {
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info->notes_files = info->notes + info->numnote;
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info->numnote++;
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}
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@ -55,6 +55,7 @@
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#include <trace/events/sched.h>
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static bool dump_vma_snapshot(struct coredump_params *cprm);
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static void free_vma_snapshot(struct coredump_params *cprm);
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static int core_uses_pid;
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static unsigned int core_pipe_limit;
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@ -765,7 +766,7 @@ void do_coredump(const kernel_siginfo_t *siginfo)
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dump_emit(&cprm, "", 1);
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}
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file_end_write(cprm.file);
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kvfree(cprm.vma_meta);
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free_vma_snapshot(&cprm);
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}
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if (ispipe && core_pipe_limit)
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wait_for_dump_helpers(cprm.file);
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@ -1099,6 +1100,20 @@ static struct vm_area_struct *next_vma(struct vm_area_struct *this_vma,
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return gate_vma;
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}
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static void free_vma_snapshot(struct coredump_params *cprm)
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{
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if (cprm->vma_meta) {
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int i;
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for (i = 0; i < cprm->vma_count; i++) {
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struct file *file = cprm->vma_meta[i].file;
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if (file)
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fput(file);
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}
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kvfree(cprm->vma_meta);
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cprm->vma_meta = NULL;
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}
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}
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/*
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* Under the mmap_lock, take a snapshot of relevant information about the task's
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* VMAs.
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@ -1135,6 +1150,11 @@ static bool dump_vma_snapshot(struct coredump_params *cprm)
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m->end = vma->vm_end;
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m->flags = vma->vm_flags;
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m->dump_size = vma_dump_size(vma, cprm->mm_flags);
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m->pgoff = vma->vm_pgoff;
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m->file = vma->vm_file;
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if (m->file)
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get_file(m->file);
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}
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mmap_write_unlock(mm);
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@ -12,6 +12,8 @@ struct core_vma_metadata {
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unsigned long start, end;
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unsigned long flags;
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unsigned long dump_size;
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unsigned long pgoff;
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struct file *file;
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};
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struct coredump_params {
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