Hello,
On Tue, Nov 15, 2022 at 10:14:44AM -0500, George Kennedy wrote:
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@googlegroups.com Signed-off-by: George Kennedy george.kennedy@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;- }
This patch is in mainline as 1b42b1a36fc946f0d7088425b90d491b4257ca3e, and backported to various stable releases.
For me this breaks
ubiattach -m 0 -O 2048
I think the check
ubi->vid_hdr_offset + UBI_VID_HDR_SIZE > ubi->vid_hdr_alsize
is wrong. Without -O passed to ubiattach (and dynamic debug enabled) I get:
[ 5294.936762] UBI DBG gen (pid 9619): sizeof(struct ubi_ainf_peb) 56 [ 5294.936769] UBI DBG gen (pid 9619): sizeof(struct ubi_wl_entry) 32 [ 5294.936774] UBI DBG gen (pid 9619): min_io_size 2048 [ 5294.936779] UBI DBG gen (pid 9619): max_write_size 2048 [ 5294.936783] UBI DBG gen (pid 9619): hdrs_min_io_size 512 [ 5294.936787] UBI DBG gen (pid 9619): ec_hdr_alsize 512 [ 5294.936791] UBI DBG gen (pid 9619): vid_hdr_alsize 512 [ 5294.936796] UBI DBG gen (pid 9619): vid_hdr_offset 512 [ 5294.936800] UBI DBG gen (pid 9619): vid_hdr_aloffset 512 [ 5294.936804] UBI DBG gen (pid 9619): vid_hdr_shift 0 [ 5294.936808] UBI DBG gen (pid 9619): leb_start 2048 [ 5294.936812] UBI DBG gen (pid 9619): max_erroneous 409
So the check would only pass for vid_hdr_offset <= 512 - UBI_VID_HDR_SIZE; note that even specifying the default value 512 (i.e.
ubiattach -m 0 -O 512
) fails the check.
A less strong check would be:
diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c index 0904eb40c95f..69c28a862430 100644 --- a/drivers/mtd/ubi/build.c +++ b/drivers/mtd/ubi/build.c @@ -666,8 +666,8 @@ 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)) { + if (ubi->vid_hdr_offset && + ubi->vid_hdr_offset + UBI_VID_HDR_SIZE > ubi->peb_size) { ubi_err(ubi, "VID header offset %d too large.", ubi->vid_hdr_offset); return -EINVAL; }
But I'm unsure if this would be too lax?!
Best regards Uwe