vmcore: fix PT_NOTE n_namesz, n_descsz overflow issue

When updating PT_NOTE header size (ie.  p_memsz), an overflow issue
happens with the following bogus note entry:

  n_namesz = 0xFFFFFFFF
  n_descsz = 0x0
  n_type   = 0x0

This kind of note entry should be dropped during updating p_memsz.  But
because n_namesz is 32bit, after (n_namesz + 3) & (~3), it's overflow to
0x0, the note entry size looks sane and reserved.

When userspace (eg.  crash utility) is trying to access such bogus note,
it could lead to an unexpected behavior (eg.  crash utility segment fault
because it's reading bogus address).

The source of bogus note hasn't been identified yet.  At least we could
drop the bogus note so user space wouldn't be surprised.

Signed-off-by: WANG Chao <[email protected]>
Cc: Dave Anderson <[email protected]>
Cc: Baoquan He <[email protected]>
Cc: Randy Wright <[email protected]>
Cc: Vivek Goyal <[email protected]>
Cc: Paul Gortmaker <[email protected]>
Cc: Fabian Frederick <[email protected]>
Cc: Vitaly Kuznetsov <[email protected]>
Cc: Rashika Kheria <[email protected]>
Cc: Greg Pearson <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 4 insertions, 4 deletions

diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index a90d6d354199..4e61388ec03d 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -546,8 +546,8 @@ static int __init update_note_header_size_elf64(const Elf64_Ehdr *ehdr_ptr)
 		nhdr_ptr = notes_section;
 		while (nhdr_ptr->n_namesz != 0) {
 			sz = sizeof(Elf64_Nhdr) +
-				((nhdr_ptr->n_namesz + 3) & ~3) +
-				((nhdr_ptr->n_descsz + 3) & ~3);
+				(((u64)nhdr_ptr->n_namesz + 3) & ~3) +
+				(((u64)nhdr_ptr->n_descsz + 3) & ~3);
 			if ((real_sz + sz) > max_sz) {
 				pr_warn("Warning: Exceeded p_memsz, dropping PT_NOTE entry n_namesz=0x%x, n_descsz=0x%x\n",
 					nhdr_ptr->n_namesz, nhdr_ptr->n_descsz);
@@ -732,8 +732,8 @@ static int __init update_note_header_size_elf32(const Elf32_Ehdr *ehdr_ptr)
 		nhdr_ptr = notes_section;
 		while (nhdr_ptr->n_namesz != 0) {
 			sz = sizeof(Elf32_Nhdr) +
-				((nhdr_ptr->n_namesz + 3) & ~3) +
-				((nhdr_ptr->n_descsz + 3) & ~3);
+				(((u64)nhdr_ptr->n_namesz + 3) & ~3) +
+				(((u64)nhdr_ptr->n_descsz + 3) & ~3);
 			if ((real_sz + sz) > max_sz) {
 				pr_warn("Warning: Exceeded p_memsz, dropping PT_NOTE entry n_namesz=0x%x, n_descsz=0x%x\n",
 					nhdr_ptr->n_namesz, nhdr_ptr->n_descsz);