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authorJann Horn <jannh@google.com>2022-01-26 05:57:39 +0300
committerKees Cook <keescook@chromium.org>2022-03-02 03:16:26 +0300
commit84158b7f6a0624b81800b4e7c90f7fb7fdecf66c (patch)
tree92420ed5ec7ee5ab9a87e97bd13fe4e07d3e0561 /fs/coredump.c
parent10b19249192ae28ee9092ceca327a83d27d88bd0 (diff)
downloadlinux-84158b7f6a0624b81800b4e7c90f7fb7fdecf66c.tar.xz
coredump: Also dump first pages of non-executable ELF libraries
When I rewrote the VMA dumping logic for coredumps, I changed it to recognize ELF library mappings based on the file being executable instead of the mapping having an ELF header. But turns out, distros ship many ELF libraries as non-executable, so the heuristic goes wrong... Restore the old behavior where FILTER(ELF_HEADERS) dumps the first page of any offset-0 readable mapping that starts with the ELF magic. This fix is technically layer-breaking a bit, because it checks for something ELF-specific in fs/coredump.c; but since we probably want to share this between standard ELF and FDPIC ELF anyway, I guess it's fine? And this also keeps the change small for backporting. Cc: stable@vger.kernel.org Fixes: 429a22e776a2 ("coredump: rework elf/elf_fdpic vma_dump_size() into common helper") Reported-by: Bill Messmer <wmessmer@microsoft.com> Signed-off-by: Jann Horn <jannh@google.com> Signed-off-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20220126025739.2014888-1-jannh@google.com
Diffstat (limited to 'fs/coredump.c')
-rw-r--r--fs/coredump.c39
1 files changed, 34 insertions, 5 deletions
diff --git a/fs/coredump.c b/fs/coredump.c
index 1c060c0a2d72..b73817712dd2 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -42,6 +42,7 @@
#include <linux/path.h>
#include <linux/timekeeping.h>
#include <linux/sysctl.h>
+#include <linux/elf.h>
#include <linux/uaccess.h>
#include <asm/mmu_context.h>
@@ -980,6 +981,8 @@ static bool always_dump_vma(struct vm_area_struct *vma)
return false;
}
+#define DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER 1
+
/*
* Decide how much of @vma's contents should be included in a core dump.
*/
@@ -1039,9 +1042,20 @@ static unsigned long vma_dump_size(struct vm_area_struct *vma,
* 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) &&
- (READ_ONCE(file_inode(vma->vm_file)->i_mode) & 0111) != 0)
- return PAGE_SIZE;
+ vma->vm_pgoff == 0 && (vma->vm_flags & VM_READ)) {
+ if ((READ_ONCE(file_inode(vma->vm_file)->i_mode) & 0111) != 0)
+ return PAGE_SIZE;
+
+ /*
+ * ELF libraries aren't always executable.
+ * We'll want to check whether the mapping starts with the ELF
+ * magic, but not now - we're holding the mmap lock,
+ * so copy_from_user() doesn't work here.
+ * Use a placeholder instead, and fix it up later in
+ * dump_vma_snapshot().
+ */
+ return DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER;
+ }
#undef FILTER
@@ -1116,8 +1130,6 @@ int dump_vma_snapshot(struct coredump_params *cprm, int *vma_count,
m->end = vma->vm_end;
m->flags = vma->vm_flags;
m->dump_size = vma_dump_size(vma, cprm->mm_flags);
-
- vma_data_size += m->dump_size;
}
mmap_write_unlock(mm);
@@ -1127,6 +1139,23 @@ int dump_vma_snapshot(struct coredump_params *cprm, int *vma_count,
return -EFAULT;
}
+ for (i = 0; i < *vma_count; i++) {
+ struct core_vma_metadata *m = (*vma_meta) + i;
+
+ if (m->dump_size == DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER) {
+ char elfmag[SELFMAG];
+
+ if (copy_from_user(elfmag, (void __user *)m->start, SELFMAG) ||
+ memcmp(elfmag, ELFMAG, SELFMAG) != 0) {
+ m->dump_size = 0;
+ } else {
+ m->dump_size = PAGE_SIZE;
+ }
+ }
+
+ vma_data_size += m->dump_size;
+ }
+
*vma_data_size_ptr = vma_data_size;
return 0;
}