Patch "fs/ntfs3: Fix null-ptr-deref on inode->i_op in ntfs_lookup()" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

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

to the 5.15-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:
     fs-ntfs3-fix-null-ptr-deref-on-inode-i_op-in-ntfs_lo.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 9cef343056036e96bcfdc98629134fa81f8cf8d6
Author: ZhangPeng <zhangpeng362@xxxxxxxxxx>
Date:   Fri Nov 25 10:21:59 2022 +0000

    fs/ntfs3: Fix null-ptr-deref on inode->i_op in ntfs_lookup()
    
    [ Upstream commit 254e69f284d7270e0abdc023ee53b71401c3ba0c ]
    
    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.
    
    Fixes: 4342306f0f0d ("fs/ntfs3: Add file operations and implementation")
    Reported-by: syzbot+a8f26a403c169b7593fe@xxxxxxxxxxxxxxxxxxxxxxxxx
    Signed-off-by: ZhangPeng <zhangpeng362@xxxxxxxxxx>
    Signed-off-by: Konstantin Komarov <almaz.alexandrovich@xxxxxxxxxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/ntfs3/namei.c b/fs/ntfs3/namei.c
index bc741213ad848..29fd76d94c744 100644
--- a/fs/ntfs3/namei.c
+++ b/fs/ntfs3/namei.c
@@ -86,6 +86,16 @@ 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);
 }