FAILED: patch "[PATCH] fs/ntfs3: Fix null-ptr-deref on inode->i_op in ntfs_lookup()" failed to apply to 6.2-stable tree

The patch below does not apply to the 6.2-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.2.y
git checkout FETCH_HEAD
git cherry-pick -x 254e69f284d7270e0abdc023ee53b71401c3ba0c
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2023051138-refueling-ought-706e@gregkh' --subject-prefix 'PATCH 6.2.y' HEAD^..

Possible dependencies:

254e69f284d7 ("fs/ntfs3: Fix null-ptr-deref on inode->i_op in ntfs_lookup()")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 254e69f284d7270e0abdc023ee53b71401c3ba0c Mon Sep 17 00:00:00 2001
From: ZhangPeng <[email protected]>
Date: Fri, 25 Nov 2022 10:21:59 +0000
Subject: [PATCH] fs/ntfs3: Fix null-ptr-deref on inode->i_op in ntfs_lookup()

Syzbot reported a null-ptr-deref bug:

ntfs3: loop0: Different NTFS' sector size (1024) and media sector size
(512)
ntfs3: loop0: Mark volume as dirty due to NTFS errors

general protection fault, probably for non-canonical address
0xdffffc0000000001: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
RIP: 0010:d_flags_for_inode fs/dcache.c:1980 [inline]
RIP: 0010:__d_add+0x5ce/0x800 fs/dcache.c:2796
Call Trace:
 <TASK>
 d_splice_alias+0x122/0x3b0 fs/dcache.c:3191
 lookup_open fs/namei.c:3391 [inline]
 open_last_lookups fs/namei.c:3481 [inline]
 path_openat+0x10e6/0x2df0 fs/namei.c:3688
 do_filp_open+0x264/0x4f0 fs/namei.c:3718
 do_sys_openat2+0x124/0x4e0 fs/open.c:1310
 do_sys_open fs/open.c:1326 [inline]
 __do_sys_open fs/open.c:1334 [inline]
 __se_sys_open fs/open.c:1330 [inline]
 __x64_sys_open+0x221/0x270 fs/open.c:1330
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

If the MFT record of ntfs inode is not a base record, inode->i_op can be NULL. And a null-ptr-deref may happen:

ntfs_lookup()

    dir_search_u() # inode->i_op is set to NULL
    d_splice_alias()
        __d_add()
            d_flags_for_inode() # inode->i_op->get_link null-ptr-deref

Fix this by adding a Check on inode->i_op before calling the d_splice_alias() function.

index 407fe92394e2..8d206770d8c6 100644
@@ -88,6 +88,16 @@ static struct dentry *ntfs_lookup(struct inode *dir, struct dentry *dentry,
 		__putname(uni);
 	}
 
+	/*
+	 * Check for a null pointer
+	 * If the MFT record of ntfs inode is not a base record, inode->i_op can be NULL.
+	 * This causes null pointer dereference in d_splice_alias().
+	 */
+	if (!IS_ERR(inode) && inode->i_op == NULL) {
+		iput(inode);
+		inode = ERR_PTR(-EINVAL);
+	}
+
 	return d_splice_alias(inode, dentry);
 }