Re: [PATCH] fs: ntfs3: Fix a possible null-pointer dereference in ni_clear()

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In a previous commit c1006bd13146, ni->mi.mrec in ni_write_inode()
could be NULL, and thus a NULL check is added for this variable.

However, in the same call stack, ni->mi.mrec can be also dereferenced
in ni_clear():

ntfs_evict_inode(inode)
   ni_write_inode(inode, ...)
     ni = ntfs_i(inode);
     is_rec_inuse(ni->mi.mrec) -> Add a NULL check by previous commit
   ni_clear(ntfs_i(inode))
     is_rec_inuse(ni->mi.mrec) -> No check

Thus, a possible null-pointer dereference may exist in ni_clear().
To fix it, a NULL check is added in this function.

Signed-off-by: Jia-Ju Bai <baijiaju1990@xxxxxxxxx>
Reported-by: TOTE Robot <oslab@xxxxxxxxxxxxxxx>
---
  fs/ntfs3/frecord.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ntfs3/frecord.c b/fs/ntfs3/frecord.c
index f1df52dfab74..046ec4179d75 100644
--- a/fs/ntfs3/frecord.c
+++ b/fs/ntfs3/frecord.c
@@ -102,7 +102,7 @@ void ni_clear(struct ntfs_inode *ni)
  {
  	struct rb_node *node;
- if (!ni->vfs_inode.i_nlink && is_rec_inuse(ni->mi.mrec))
+	if (!ni->vfs_inode.i_nlink && ni->mi.mrec && is_rec_inuse(ni->mi.mrec))
  		ni_delete_all(ni);
al_destroy(ni);

I apologize for the delayed response.

Thank you for your work, applied!





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