[PATCH] ubi: ensure that VID header offset + VID header size <= alloc, size

[George Kennedy]

Ensure that the VID header offset + VID header size does not exceed
the allocated area to avoid slab OOB.

BUG: KASAN: slab-out-of-bounds in crc32_body lib/crc32.c:111 [inline]
BUG: KASAN: slab-out-of-bounds in crc32_le_generic lib/crc32.c:179 [inline]
BUG: KASAN: slab-out-of-bounds in crc32_le_base+0x58c/0x626 lib/crc32.c:197
Read of size 4 at addr ffff88802bb36f00 by task syz-executor136/1555

CPU: 2 PID: 1555 Comm: syz-executor136 Tainted: G        W
6.0.0-1868 #1
Hardware name: Red Hat KVM, BIOS 1.13.0-2.module+el8.3.0+7860+a7792d29
04/01/2014
Call Trace:
  <TASK>
  __dump_stack lib/dump_stack.c:88 [inline]
  dump_stack_lvl+0x85/0xad lib/dump_stack.c:106
  print_address_description mm/kasan/report.c:317 [inline]
  print_report.cold.13+0xb6/0x6bb mm/kasan/report.c:433
  kasan_report+0xa7/0x11b mm/kasan/report.c:495
  crc32_body lib/crc32.c:111 [inline]
  crc32_le_generic lib/crc32.c:179 [inline]
  crc32_le_base+0x58c/0x626 lib/crc32.c:197
  ubi_io_write_vid_hdr+0x1b7/0x472 drivers/mtd/ubi/io.c:1067
  create_vtbl+0x4d5/0x9c4 drivers/mtd/ubi/vtbl.c:317
  create_empty_lvol drivers/mtd/ubi/vtbl.c:500 [inline]
  ubi_read_volume_table+0x67b/0x288a drivers/mtd/ubi/vtbl.c:812
  ubi_attach+0xf34/0x1603 drivers/mtd/ubi/attach.c:1601
  ubi_attach_mtd_dev+0x6f3/0x185e drivers/mtd/ubi/build.c:965
  ctrl_cdev_ioctl+0x2db/0x347 drivers/mtd/ubi/cdev.c:1043
  vfs_ioctl fs/ioctl.c:51 [inline]
  __do_sys_ioctl fs/ioctl.c:870 [inline]
  __se_sys_ioctl fs/ioctl.c:856 [inline]
  __x64_sys_ioctl+0x193/0x213 fs/ioctl.c:856
  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
  do_syscall_64+0x3e/0x86 arch/x86/entry/common.c:80
  entry_SYSCALL_64_after_hwframe+0x63/0x0
RIP: 0033:0x7f96d5cf753d
Code:
RSP: 002b:00007fffd72206f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f96d5cf753d
RDX: 0000000020000080 RSI: 0000000040186f40 RDI: 0000000000000003
RBP: 0000000000400cd0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000400be0
R13: 00007fffd72207e0 R14: 0000000000000000 R15: 0000000000000000
  </TASK>

Allocated by task 1555:
  kasan_save_stack+0x20/0x3d mm/kasan/common.c:38
  kasan_set_track mm/kasan/common.c:45 [inline]
  set_alloc_info mm/kasan/common.c:437 [inline]
  ____kasan_kmalloc mm/kasan/common.c:516 [inline]
  __kasan_kmalloc+0x88/0xa3 mm/kasan/common.c:525
  kasan_kmalloc include/linux/kasan.h:234 [inline]
  __kmalloc+0x138/0x257 mm/slub.c:4429
  kmalloc include/linux/slab.h:605 [inline]
  ubi_alloc_vid_buf drivers/mtd/ubi/ubi.h:1093 [inline]
  create_vtbl+0xcc/0x9c4 drivers/mtd/ubi/vtbl.c:295
  create_empty_lvol drivers/mtd/ubi/vtbl.c:500 [inline]
  ubi_read_volume_table+0x67b/0x288a drivers/mtd/ubi/vtbl.c:812
  ubi_attach+0xf34/0x1603 drivers/mtd/ubi/attach.c:1601
  ubi_attach_mtd_dev+0x6f3/0x185e drivers/mtd/ubi/build.c:965
  ctrl_cdev_ioctl+0x2db/0x347 drivers/mtd/ubi/cdev.c:1043
  vfs_ioctl fs/ioctl.c:51 [inline]
  __do_sys_ioctl fs/ioctl.c:870 [inline]
  __se_sys_ioctl fs/ioctl.c:856 [inline]
  __x64_sys_ioctl+0x193/0x213 fs/ioctl.c:856
  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
  do_syscall_64+0x3e/0x86 arch/x86/entry/common.c:80
  entry_SYSCALL_64_after_hwframe+0x63/0x0

The buggy address belongs to the object at ffff88802bb36e00
  which belongs to the cache kmalloc-256 of size 256
The buggy address is located 0 bytes to the right of
  256-byte region [ffff88802bb36e00, ffff88802bb36f00)

The buggy address belongs to the physical page:
page:00000000ea4d1263 refcount:1 mapcount:0 mapping:0000000000000000
index:0x0 pfn:0x2bb36
head:00000000ea4d1263 order:1 compound_mapcount:0 compound_pincount:0
flags: 0xfffffc0010200(slab|head|node=0|zone=1|lastcpupid=0x1fffff)
raw: 000fffffc0010200 ffffea000066c300 dead000000000003 ffff888100042b40
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff88802bb36e00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  ffff88802bb36e80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88802bb36f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                    ^
  ffff88802bb36f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  ffff88802bb37000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Fixes: 801c135ce73d ("UBI: Unsorted Block Images")
Reported-by: syzkaller <syzkaller at googlegroups.com>
Signed-off-by: George Kennedy <george.kennedy at oracle.com>
---
  drivers/mtd/ubi/build.c | 6 ++++++
  1 file changed, 6 insertions(+)

diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c
index a32050fecabf..53aa4de6b963 100644
--- a/drivers/mtd/ubi/build.c
+++ b/drivers/mtd/ubi/build.c
@@ -663,6 +663,12 @@ static int io_init(struct ubi_device *ubi, int max_beb_per1024)
  	ubi->ec_hdr_alsize = ALIGN(UBI_EC_HDR_SIZE, ubi->hdrs_min_io_size);
  	ubi->vid_hdr_alsize = ALIGN(UBI_VID_HDR_SIZE, ubi->hdrs_min_io_size);
  
+	if (ubi->vid_hdr_offset && ((ubi->vid_hdr_offset + UBI_VID_HDR_SIZE) >
+	    ubi->vid_hdr_alsize)) {
+		ubi_err(ubi, "VID header offset %d too large.", ubi->vid_hdr_offset);
+		return -EINVAL;
+	}
+
  	dbg_gen("min_io_size      %d", ubi->min_io_size);
  	dbg_gen("max_write_size   %d", ubi->max_write_size);
  	dbg_gen("hdrs_min_io_size %d", ubi->hdrs_min_io_size);
-- 
2.31.1