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authorEric W. Biederman <ebiederm@xmission.com>2022-03-08 13:04:19 -0600
committerEric W. Biederman <ebiederm@xmission.com>2022-03-08 13:04:19 -0600
commit390031c942116d4733310f0684beb8db19885fe6 (patch)
treee9f3a4fbb850a5c973b31d66eb77878065fd71aa
parent9ec7d3230717b4fe9b6c7afeb4811909c23fa1d7 (diff)
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: a07279c9a8cd ("binfmt_elf, binfmt_elf_fdpic: use a VMA list snapshot") Fixes: 2aa362c49c31 ("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>
-rw-r--r--fs/binfmt_elf.c24
-rw-r--r--fs/coredump.c22
-rw-r--r--include/linux/coredump.h2
3 files changed, 35 insertions, 13 deletions
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 7f0c391832cf..ca5296cae979 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1641,17 +1641,16 @@ static void fill_siginfo_note(struct memelfnote *note, user_siginfo_t *csigdata,
* long file_ofs
* followed by COUNT filenames in ASCII: "FILE1" NUL "FILE2" NUL...
*/
-static int fill_files_note(struct memelfnote *note)
+static int fill_files_note(struct memelfnote *note, struct coredump_params *cprm)
{
- struct mm_struct *mm = current->mm;
- struct vm_area_struct *vma;
unsigned count, size, names_ofs, remaining, n;
user_long_t *data;
user_long_t *start_end_ofs;
char *name_base, *name_curpos;
+ int i;
/* *Estimated* file count and total data size needed */
- count = mm->map_count;
+ count = cprm->vma_count;
if (count > UINT_MAX / 64)
return -EINVAL;
size = count * 64;
@@ -1673,11 +1672,12 @@ static int fill_files_note(struct memelfnote *note)
name_base = name_curpos = ((char *)data) + names_ofs;
remaining = size - names_ofs;
count = 0;
- for (vma = mm->mmap; vma != NULL; vma = vma->vm_next) {
+ for (i = 0; i < cprm->vma_count; i++) {
+ struct core_vma_metadata *m = &cprm->vma_meta[i];
struct file *file;
const char *filename;
- file = vma->vm_file;
+ file = m->file;
if (!file)
continue;
filename = file_path(file, name_curpos, remaining);
@@ -1697,9 +1697,9 @@ static int fill_files_note(struct memelfnote *note)
memmove(name_curpos, filename, n);
name_curpos += n;
- *start_end_ofs++ = vma->vm_start;
- *start_end_ofs++ = vma->vm_end;
- *start_end_ofs++ = vma->vm_pgoff;
+ *start_end_ofs++ = m->start;
+ *start_end_ofs++ = m->end;
+ *start_end_ofs++ = m->pgoff;
count++;
}
@@ -1710,7 +1710,7 @@ static int fill_files_note(struct memelfnote *note)
* Count usually is less than mm->map_count,
* we need to move filenames down.
*/
- n = mm->map_count - count;
+ n = cprm->vma_count - count;
if (n != 0) {
unsigned shift_bytes = n * 3 * sizeof(data[0]);
memmove(name_base - shift_bytes, name_base,
@@ -1909,7 +1909,7 @@ static int fill_note_info(struct elfhdr *elf, int phdrs,
fill_auxv_note(&info->auxv, current->mm);
info->size += notesize(&info->auxv);
- if (fill_files_note(&info->files) == 0)
+ if (fill_files_note(&info->files, cprm) == 0)
info->size += notesize(&info->files);
return 1;
@@ -2098,7 +2098,7 @@ static int fill_note_info(struct elfhdr *elf, int phdrs,
fill_auxv_note(info->notes + 3, current->mm);
info->numnote = 4;
- if (fill_files_note(info->notes + info->numnote) == 0) {
+ if (fill_files_note(info->notes + info->numnote, cprm) == 0) {
info->notes_files = info->notes + info->numnote;
info->numnote++;
}
diff --git a/fs/coredump.c b/fs/coredump.c
index 7f100a637264..7ed7d601e5e0 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -55,6 +55,7 @@
#include <trace/events/sched.h>
static bool dump_vma_snapshot(struct coredump_params *cprm);
+static void free_vma_snapshot(struct coredump_params *cprm);
static int core_uses_pid;
static unsigned int core_pipe_limit;
@@ -765,7 +766,7 @@ void do_coredump(const kernel_siginfo_t *siginfo)
dump_emit(&cprm, "", 1);
}
file_end_write(cprm.file);
- kvfree(cprm.vma_meta);
+ free_vma_snapshot(&cprm);
}
if (ispipe && core_pipe_limit)
wait_for_dump_helpers(cprm.file);
@@ -1099,6 +1100,20 @@ static struct vm_area_struct *next_vma(struct vm_area_struct *this_vma,
return gate_vma;
}
+static void free_vma_snapshot(struct coredump_params *cprm)
+{
+ if (cprm->vma_meta) {
+ int i;
+ for (i = 0; i < cprm->vma_count; i++) {
+ struct file *file = cprm->vma_meta[i].file;
+ if (file)
+ fput(file);
+ }
+ kvfree(cprm->vma_meta);
+ cprm->vma_meta = NULL;
+ }
+}
+
/*
* Under the mmap_lock, take a snapshot of relevant information about the task's
* VMAs.
@@ -1135,6 +1150,11 @@ static bool dump_vma_snapshot(struct coredump_params *cprm)
m->end = vma->vm_end;
m->flags = vma->vm_flags;
m->dump_size = vma_dump_size(vma, cprm->mm_flags);
+ m->pgoff = vma->vm_pgoff;
+
+ m->file = vma->vm_file;
+ if (m->file)
+ get_file(m->file);
}
mmap_write_unlock(mm);
diff --git a/include/linux/coredump.h b/include/linux/coredump.h
index 7d05370e555e..08a1d3e7e46d 100644
--- a/include/linux/coredump.h
+++ b/include/linux/coredump.h
@@ -12,6 +12,8 @@ struct core_vma_metadata {
unsigned long start, end;
unsigned long flags;
unsigned long dump_size;
+ unsigned long pgoff;
+ struct file *file;
};
struct coredump_params {