This is a note to let you know that I've just added the patch titled ntfs: fix out-of-bounds read in ntfs_attr_find() to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: ntfs-fix-out-of-bounds-read-in-ntfs_attr_find.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 36a4d82dddbbd421d2b8e79e1cab68c8126d5075 Mon Sep 17 00:00:00 2001 From: Hawkins Jiawei <yin31149@xxxxxxxxx> Date: Thu, 1 Sep 2022 00:09:36 +0800 Subject: ntfs: fix out-of-bounds read in ntfs_attr_find() From: Hawkins Jiawei <yin31149@xxxxxxxxx> commit 36a4d82dddbbd421d2b8e79e1cab68c8126d5075 upstream. Kernel iterates over ATTR_RECORDs in mft record in ntfs_attr_find(). To ensure access on these ATTR_RECORDs are within bounds, kernel will do some checking during iteration. The problem is that during checking whether ATTR_RECORD's name is within bounds, kernel will dereferences the ATTR_RECORD name_offset field, before checking this ATTR_RECORD strcture is within bounds. This problem may result out-of-bounds read in ntfs_attr_find(), reported by Syzkaller: ================================================================== BUG: KASAN: use-after-free in ntfs_attr_find+0xc02/0xce0 fs/ntfs/attrib.c:597 Read of size 2 at addr ffff88807e352009 by task syz-executor153/3607 [...] Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:317 [inline] print_report.cold+0x2ba/0x719 mm/kasan/report.c:433 kasan_report+0xb1/0x1e0 mm/kasan/report.c:495 ntfs_attr_find+0xc02/0xce0 fs/ntfs/attrib.c:597 ntfs_attr_lookup+0x1056/0x2070 fs/ntfs/attrib.c:1193 ntfs_read_inode_mount+0x89a/0x2580 fs/ntfs/inode.c:1845 ntfs_fill_super+0x1799/0x9320 fs/ntfs/super.c:2854 mount_bdev+0x34d/0x410 fs/super.c:1400 legacy_get_tree+0x105/0x220 fs/fs_context.c:610 vfs_get_tree+0x89/0x2f0 fs/super.c:1530 do_new_mount fs/namespace.c:3040 [inline] path_mount+0x1326/0x1e20 fs/namespace.c:3370 do_mount fs/namespace.c:3383 [inline] __do_sys_mount fs/namespace.c:3591 [inline] __se_sys_mount fs/namespace.c:3568 [inline] __x64_sys_mount+0x27f/0x300 fs/namespace.c:3568 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd [...] </TASK> The buggy address belongs to the physical page: page:ffffea0001f8d400 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7e350 head:ffffea0001f8d400 order:3 compound_mapcount:0 compound_pincount:0 flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff) raw: 00fff00000010200 0000000000000000 dead000000000122 ffff888011842140 raw: 0000000000000000 0000000000040004 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff88807e351f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88807e351f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff88807e352000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88807e352080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88807e352100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== This patch solves it by moving the ATTR_RECORD strcture's bounds checking earlier, then checking whether ATTR_RECORD's name is within bounds. What's more, this patch also add some comments to improve its maintainability. Link: https://lkml.kernel.org/r/20220831160935.3409-3-yin31149@xxxxxxxxx Link: https://lore.kernel.org/all/1636796c-c85e-7f47-e96f-e074fee3c7d3@xxxxxxxxxx/ Link: https://groups.google.com/g/syzkaller-bugs/c/t_XdeKPGTR4/m/LECAuIGcBgAJ Signed-off-by: chenxiaosong (A) <chenxiaosong2@xxxxxxxxxx> Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx> Signed-off-by: Hawkins Jiawei <yin31149@xxxxxxxxx> Reported-by: syzbot+5f8dcabe4a3b2c51c607@xxxxxxxxxxxxxxxxxxxxxxxxx Tested-by: syzbot+5f8dcabe4a3b2c51c607@xxxxxxxxxxxxxxxxxxxxxxxxx Cc: Anton Altaparmakov <anton@xxxxxxxxxx> Cc: syzkaller-bugs <syzkaller-bugs@xxxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/ntfs/attrib.c | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-) --- a/fs/ntfs/attrib.c +++ b/fs/ntfs/attrib.c @@ -608,11 +608,23 @@ static int ntfs_attr_find(const ATTR_TYP for (;; a = (ATTR_RECORD*)((u8*)a + le32_to_cpu(a->length))) { u8 *mrec_end = (u8 *)ctx->mrec + le32_to_cpu(ctx->mrec->bytes_allocated); - u8 *name_end = (u8 *)a + le16_to_cpu(a->name_offset) + - a->name_length * sizeof(ntfschar); - if ((u8*)a < (u8*)ctx->mrec || (u8*)a > mrec_end || - name_end > mrec_end) + u8 *name_end; + + /* check whether ATTR_RECORD wrap */ + if ((u8 *)a < (u8 *)ctx->mrec) break; + + /* check whether Attribute Record Header is within bounds */ + if ((u8 *)a > mrec_end || + (u8 *)a + sizeof(ATTR_RECORD) > mrec_end) + break; + + /* check whether ATTR_RECORD's name is within bounds */ + name_end = (u8 *)a + le16_to_cpu(a->name_offset) + + a->name_length * sizeof(ntfschar); + if (name_end > mrec_end) + break; + ctx->attr = a; if (unlikely(le32_to_cpu(a->type) > le32_to_cpu(type) || a->type == AT_END)) Patches currently in stable-queue which might be from yin31149@xxxxxxxxx are queue-4.9/ntfs-check-overflow-when-iterating-attr_records.patch queue-4.9/ntfs-fix-out-of-bounds-read-in-ntfs_attr_find.patch queue-4.9/ntfs-fix-use-after-free-in-ntfs_attr_find.patch