[RFC RFT PATCH] ocfs2: Invalidate inode if i_mode is zero after block read

[RFC RFT PATCH] ocfs2: Invalidate inode if i_mode is zero after block read

[Ahmet Eray Karadag]

A panic occurs in ocfs2_unlink due to WARN_ON(inode->i_nlink == 0) when
handling a corrupted inode with i_mode=0 and i_nlink=0 in memory.

This "zombie" inode is created because ocfs2_read_locked_inode proceeds
even after ocfs2_validate_inode_block successfully validates a block
that structurally looks okay (passes checksum, signature etc.) but
contains semantically invalid data (specifically i_mode=0). The current
validation function doesn't check for i_mode being zero.

This results in an in-memory inode with i_mode=0 being added to the VFS
cache, which later triggers the panic during unlink.

Prevent this by adding an explicit check for i_mode == 0 within
ocfs2_validate_inode_block. If i_mode is zero, return -EFSCORRUPTED to signal
corruption. This causes the caller (ocfs2_read_locked_inode) to invoke
make_bad_inode(), correctly preventing the zombie inode from entering
the cache.

---
[RFC]:
The current fix handles i_mode=0 corruption detected during inode read
by returning -EFSCORRUPTED from ocfs2_validate_inode_block, which leads to
make_bad_inode() being called, preventing the corrupted inode from
entering the cache. This approach avoids immediately forcing the entire
filesystem read-only, assuming the corruption might be localized to
this inode.

Is this less aggressive error handling strategy appropriate for i_mode=0
corruption? Or is this condition considered severe enough that we *should*
explicitly call ocfs2_error() within the validation function to guarantee
the filesystem is marked read-only immediately upon detection?
Feedback and testing on the correct severity assessment and error
handling for this type of corruption would be appreciated.
---

Reported-by: syzbot+55c40ae8a0e5f3659f2b@syzkaller.appspotmail.com
Fixes: https://syzkaller.appspot.com/bug?extid=55c40ae8a0e5f3659f2b
Co-developed-by: Albin Babu Varghese <albinbabuvarghese20@gmail.com>
Signed-off-by: Albin Babu Varghese <albinbabuvarghese20@gmail.com>
Signed-off-by: Ahmet Eray Karadag <eraykrdg1@gmail.com>
---
 fs/ocfs2/inode.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/ocfs2/inode.c b/fs/ocfs2/inode.c
index 14bf440ea4df..d4142ff9ce65 100644
--- a/fs/ocfs2/inode.c
+++ b/fs/ocfs2/inode.c
@@ -1456,6 +1456,12 @@ int ocfs2_validate_inode_block(struct super_block *sb,
 		goto bail;
 	}
 
+	if (unlikely(le16_to_cpu(di->i_mode) == 0)) {
+		mlog(ML_ERROR, "Invalid dinode #%llu: i_mode is zero!\n",
+                           (unsigned long long)bh->b_blocknr);
+		rc = -EFSCORRUPTED;
+		goto bail;
+	}
 	/*
 	 * Errors after here are fatal.
 	 */
-- 
2.43.0

Re: [RFC RFT PATCH] ocfs2: Invalidate inode if i_mode is zero after block read

[Joseph Qi]

On 2025/10/23 06:27, Ahmet Eray Karadag wrote:
> A panic occurs in ocfs2_unlink due to WARN_ON(inode->i_nlink == 0) when
> handling a corrupted inode with i_mode=0 and i_nlink=0 in memory.
> 
> This "zombie" inode is created because ocfs2_read_locked_inode proceeds
> even after ocfs2_validate_inode_block successfully validates a block
> that structurally looks okay (passes checksum, signature etc.) but
> contains semantically invalid data (specifically i_mode=0). The current
> validation function doesn't check for i_mode being zero.
> 
> This results in an in-memory inode with i_mode=0 being added to the VFS
> cache, which later triggers the panic during unlink.
> 
> Prevent this by adding an explicit check for i_mode == 0 within
> ocfs2_validate_inode_block. If i_mode is zero, return -EFSCORRUPTED to signal
> corruption. This causes the caller (ocfs2_read_locked_inode) to invoke
> make_bad_inode(), correctly preventing the zombie inode from entering
> the cache.
> 
> ---
> [RFC]:
> The current fix handles i_mode=0 corruption detected during inode read
> by returning -EFSCORRUPTED from ocfs2_validate_inode_block, which leads to
> make_bad_inode() being called, preventing the corrupted inode from
> entering the cache. This approach avoids immediately forcing the entire
> filesystem read-only, assuming the corruption might be localized to
> this inode.
> 
> Is this less aggressive error handling strategy appropriate for i_mode=0
> corruption? Or is this condition considered severe enough that we *should*
> explicitly call ocfs2_error() within the validation function to guarantee
> the filesystem is marked read-only immediately upon detection?
> Feedback and testing on the correct severity assessment and error
> handling for this type of corruption would be appreciated.
> ---
> 
> Reported-by: syzbot+55c40ae8a0e5f3659f2b@syzkaller.appspotmail.com
> Fixes: https://syzkaller.appspot.com/bug?extid=55c40ae8a0e5f3659f2b
> Co-developed-by: Albin Babu Varghese <albinbabuvarghese20@gmail.com>
> Signed-off-by: Albin Babu Varghese <albinbabuvarghese20@gmail.com>
> Signed-off-by: Ahmet Eray Karadag <eraykrdg1@gmail.com>
> ---
>  fs/ocfs2/inode.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/fs/ocfs2/inode.c b/fs/ocfs2/inode.c
> index 14bf440ea4df..d4142ff9ce65 100644
> --- a/fs/ocfs2/inode.c
> +++ b/fs/ocfs2/inode.c
> @@ -1456,6 +1456,12 @@ int ocfs2_validate_inode_block(struct super_block *sb,
>  		goto bail;
>  	}
>  
> +	if (unlikely(le16_to_cpu(di->i_mode) == 0)) {

It seems the buggy image is carefully crafted so that it can pass the
OCFS2_VALID_FL check.
Checking i_mode here looks wried. Could we check i_links_count instead?

Thanks,
Joseph

> +		mlog(ML_ERROR, "Invalid dinode #%llu: i_mode is zero!\n",
> +                           (unsigned long long)bh->b_blocknr);
> +		rc = -EFSCORRUPTED;
> +		goto bail;
> +	}
>  	/*
>  	 * Errors after here are fatal.
>  	 */

[PATCH v2] ocfs2: Invalidate inode if i_mode is zero after block read

[Ahmet Eray Karadag]

A panic occurs in ocfs2_unlink due to WARN_ON(inode->i_nlink == 0) when
handling a corrupted inode with i_mode=0 and i_nlink=0 in memory.

This "zombie" inode is created because ocfs2_read_locked_inode proceeds
even after ocfs2_validate_inode_block successfully validates a block
that structurally looks okay (passes checksum, signature etc.) but
contains semantically invalid data (specifically i_mode=0). The current
validation function doesn't check for i_mode being zero.

This results in an in-memory inode with i_mode=0 being added to the VFS
cache, which later triggers the panic during unlink.

Prevent this by adding an explicit check for i_mode == 0 within
ocfs2_validate_inode_block. If i_mode is zero, return -EFSCORRUPTED to signal
corruption. This causes the caller (ocfs2_read_locked_inode) to invoke
make_bad_inode(), correctly preventing the zombie inode from entering
the cache.

---
[RFC]:
The current fix handles i_mode=0 corruption detected during inode read
by returning -EFSCORRUPTED from ocfs2_validate_inode_block, which leads to
make_bad_inode() being called, preventing the corrupted inode from
entering the cache. This approach avoids immediately forcing the entire
filesystem read-only, assuming the corruption might be localized to
this inode.

Is this less aggressive error handling strategy appropriate for i_mode=0
corruption? Or is this condition considered severe enough that we *should*
explicitly call ocfs2_error() within the validation function to guarantee
the filesystem is marked read-only immediately upon detection?
Feedback and testing on the correct severity assessment and error
handling for this type of corruption would be appreciated.
---
v2:
 - Reviewed how ext4 handling same situation and we come up with this
   solution
---
Reported-by: syzbot+55c40ae8a0e5f3659f2b@syzkaller.appspotmail.com
Fixes: https://syzkaller.appspot.com/bug?extid=55c40ae8a0e5f3659f2b
Co-developed-by: Albin Babu Varghese <albinbabuvarghese20@gmail.com>
Signed-off-by: Albin Babu Varghese <albinbabuvarghese20@gmail.com>
Signed-off-by: Ahmet Eray Karadag <eraykrdg1@gmail.com>
---
 fs/ocfs2/inode.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/fs/ocfs2/inode.c b/fs/ocfs2/inode.c
index 14bf440ea4df..6c936f62b169 100644
--- a/fs/ocfs2/inode.c
+++ b/fs/ocfs2/inode.c
@@ -1455,7 +1455,15 @@ int ocfs2_validate_inode_block(struct super_block *sb,
 		     (unsigned long long)bh->b_blocknr);
 		goto bail;
 	}
-
+	if (di->i_links_count == 0) {
+		if (le16_to_cpu(di->i_mode) == 0 ||
+			!(le32_to_cpu(di->i_flags) & OCFS2_ORPHANED_FL)) {
+			mlog(ML_ERROR, "Invalid dinode #%llu: i_mode is zero!\n",
+			           (unsigned long long)bh->b_blocknr);
+			rc = -EFSCORRUPTED;
+			goto bail;
+		}
+	}
 	/*
 	 * Errors after here are fatal.
 	 */
-- 
2.43.0

Re: [PATCH v2] ocfs2: Invalidate inode if i_mode is zero after block read

[Joseph Qi]

On 2025/10/24 10:30, Ahmet Eray Karadag wrote:
> A panic occurs in ocfs2_unlink due to WARN_ON(inode->i_nlink == 0) when
> handling a corrupted inode with i_mode=0 and i_nlink=0 in memory.
> 
> This "zombie" inode is created because ocfs2_read_locked_inode proceeds
> even after ocfs2_validate_inode_block successfully validates a block
> that structurally looks okay (passes checksum, signature etc.) but
> contains semantically invalid data (specifically i_mode=0). The current
> validation function doesn't check for i_mode being zero.
> 
> This results in an in-memory inode with i_mode=0 being added to the VFS
> cache, which later triggers the panic during unlink.
> 
> Prevent this by adding an explicit check for i_mode == 0 within
> ocfs2_validate_inode_block. If i_mode is zero, return -EFSCORRUPTED to signal
> corruption. This causes the caller (ocfs2_read_locked_inode) to invoke
> make_bad_inode(), correctly preventing the zombie inode from entering
> the cache.
> 
> ---
> [RFC]:
> The current fix handles i_mode=0 corruption detected during inode read
> by returning -EFSCORRUPTED from ocfs2_validate_inode_block, which leads to
> make_bad_inode() being called, preventing the corrupted inode from
> entering the cache. This approach avoids immediately forcing the entire
> filesystem read-only, assuming the corruption might be localized to
> this inode.
> 
> Is this less aggressive error handling strategy appropriate for i_mode=0
> corruption? Or is this condition considered severe enough that we *should*
> explicitly call ocfs2_error() within the validation function to guarantee
> the filesystem is marked read-only immediately upon detection?
> Feedback and testing on the correct severity assessment and error
> handling for this type of corruption would be appreciated.
> ---
> v2:
>  - Reviewed how ext4 handling same situation and we come up with this
>    solution
> ---

The version change log should be after your SOB.

> Reported-by: syzbot+55c40ae8a0e5f3659f2b@syzkaller.appspotmail.com
> Fixes: https://syzkaller.appspot.com/bug?extid=55c40ae8a0e5f3659f2b
> Co-developed-by: Albin Babu Varghese <albinbabuvarghese20@gmail.com>
> Signed-off-by: Albin Babu Varghese <albinbabuvarghese20@gmail.com>
> Signed-off-by: Ahmet Eray Karadag <eraykrdg1@gmail.com>
> ---
>  fs/ocfs2/inode.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/ocfs2/inode.c b/fs/ocfs2/inode.c
> index 14bf440ea4df..6c936f62b169 100644
> --- a/fs/ocfs2/inode.c
> +++ b/fs/ocfs2/inode.c
> @@ -1455,7 +1455,15 @@ int ocfs2_validate_inode_block(struct super_block *sb,
>  		     (unsigned long long)bh->b_blocknr);
>  		goto bail;
>  	}
> -
> +	if (di->i_links_count == 0) {
> +		if (le16_to_cpu(di->i_mode) == 0 ||
> +			!(le32_to_cpu(di->i_flags) & OCFS2_ORPHANED_FL)) {

Why not put those in a single check?
BTW, i_links_count is little endian and should convert to host endian first.
And we'd prefer the following alignment:

if (!le16_to_cpu(di->i_links_count) && !le16_to_cpu(di->i_mode) &&
    !(le32_to_cpu(di->i_flags) & OCFS2_ORPHANED_FL))
	......

Thanks,
Joseph


> +			mlog(ML_ERROR, "Invalid dinode #%llu: i_mode is zero!\n",
> +			           (unsigned long long)bh->b_blocknr);
> +			rc = -EFSCORRUPTED;
> +			goto bail;
> +		}
> +	}
>  	/*
>  	 * Errors after here are fatal.
>  	 */

[PATCH v3] ocfs2: Invalidate inode if i_mode is zero after block read

[Ahmet Eray Karadag]

A panic occurs in ocfs2_unlink due to WARN_ON(inode->i_nlink == 0) when
handling a corrupted inode with i_mode=0 and i_nlink=0 in memory.

This "zombie" inode is created because ocfs2_read_locked_inode proceeds
even after ocfs2_validate_inode_block successfully validates a block
that structurally looks okay (passes checksum, signature etc.) but
contains semantically invalid data (specifically i_mode=0). The current
validation function doesn't check for i_mode being zero.

This results in an in-memory inode with i_mode=0 being added to the VFS
cache, which later triggers the panic during unlink.

Prevent this by adding an explicit check for i_mode == 0 within
ocfs2_validate_inode_block. If i_mode is zero, return -EFSCORRUPTED to signal
corruption. This causes the caller (ocfs2_read_locked_inode) to invoke
make_bad_inode(), correctly preventing the zombie inode from entering
the cache.

---
[RFC]:
The current fix handles i_mode=0 corruption detected during inode read
by returning -EFSCORRUPTED from ocfs2_validate_inode_block, which leads to
make_bad_inode() being called, preventing the corrupted inode from
entering the cache. This approach avoids immediately forcing the entire
filesystem read-only, assuming the corruption might be localized to
this inode.

Is this less aggressive error handling strategy appropriate for i_mode=0
corruption? Or is this condition considered severe enough that we *should*
explicitly call ocfs2_error() within the validation function to guarantee
the filesystem is marked read-only immediately upon detection?
Feedback and testing on the correct severity assessment and error
handling for this type of corruption would be appreciated.

Reported-by: syzbot+55c40ae8a0e5f3659f2b@syzkaller.appspotmail.com
Fixes: https://syzkaller.appspot.com/bug?extid=55c40ae8a0e5f3659f2b
Co-developed-by: Albin Babu Varghese <albinbabuvarghese20@gmail.com>
Signed-off-by: Albin Babu Varghese <albinbabuvarghese20@gmail.com>
Signed-off-by: Ahmet Eray Karadag <eraykrdg1@gmail.com>
---
v2:
 - Reviewed how ext4 handling same situation and we come up with this
   solution
---
v3:
 - Implement combined check for nlink=0, mode=0 and non-orphan
   as requested.
---
 fs/ocfs2/inode.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/fs/ocfs2/inode.c b/fs/ocfs2/inode.c
index 14bf440ea4df..3feeaa475b62 100644
--- a/fs/ocfs2/inode.c
+++ b/fs/ocfs2/inode.c
@@ -1455,7 +1455,14 @@ int ocfs2_validate_inode_block(struct super_block *sb,
 		     (unsigned long long)bh->b_blocknr);
 		goto bail;
 	}
-
+	if (!le16_to_cpu(di->i_links_count) && !le16_to_cpu(di->i_mode) &&
+		!(le32_to_cpu(di->i_flags) & OCFS2_ORPHANED_FL)) {
+			mlog(ML_ERROR, "Invalid dinode #%llu: "
+				"Corrupt state (nlink=0, mode=0, !orphan) detected!\n",
+			        (unsigned long long)bh->b_blocknr);
+			rc = -EFSCORRUPTED;
+			goto bail;
+	}
 	/*
 	 * Errors after here are fatal.
 	 */
-- 
2.43.0

Re: [PATCH v3] ocfs2: Invalidate inode if i_mode is zero after block read

[Joseph Qi]

On 2025/10/25 19:13, Ahmet Eray Karadag wrote:
> A panic occurs in ocfs2_unlink due to WARN_ON(inode->i_nlink == 0) when
> handling a corrupted inode with i_mode=0 and i_nlink=0 in memory.
> 
> This "zombie" inode is created because ocfs2_read_locked_inode proceeds
> even after ocfs2_validate_inode_block successfully validates a block
> that structurally looks okay (passes checksum, signature etc.) but
> contains semantically invalid data (specifically i_mode=0). The current
> validation function doesn't check for i_mode being zero.
> 
> This results in an in-memory inode with i_mode=0 being added to the VFS
> cache, which later triggers the panic during unlink.
> 
> Prevent this by adding an explicit check for i_mode == 0 within
> ocfs2_validate_inode_block. If i_mode is zero, return -EFSCORRUPTED to signal
> corruption. This causes the caller (ocfs2_read_locked_inode) to invoke
> make_bad_inode(), correctly preventing the zombie inode from entering
> the cache.
> 
> ---
> [RFC]:
> The current fix handles i_mode=0 corruption detected during inode read
> by returning -EFSCORRUPTED from ocfs2_validate_inode_block, which leads to
> make_bad_inode() being called, preventing the corrupted inode from
> entering the cache. This approach avoids immediately forcing the entire
> filesystem read-only, assuming the corruption might be localized to
> this inode.
> 
> Is this less aggressive error handling strategy appropriate for i_mode=0
> corruption? Or is this condition considered severe enough that we *should*
> explicitly call ocfs2_error() within the validation function to guarantee
> the filesystem is marked read-only immediately upon detection?
> Feedback and testing on the correct severity assessment and error
> handling for this type of corruption would be appreciated.
> 
> Reported-by: syzbot+55c40ae8a0e5f3659f2b@syzkaller.appspotmail.com
> Fixes: https://syzkaller.appspot.com/bug?extid=55c40ae8a0e5f3659f2b
> Co-developed-by: Albin Babu Varghese <albinbabuvarghese20@gmail.com>
> Signed-off-by: Albin Babu Varghese <albinbabuvarghese20@gmail.com>
> Signed-off-by: Ahmet Eray Karadag <eraykrdg1@gmail.com>
> ---
> v2:
>  - Reviewed how ext4 handling same situation and we come up with this
>    solution
> ---
> v3:
>  - Implement combined check for nlink=0, mode=0 and non-orphan
>    as requested.
> ---
>  fs/ocfs2/inode.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/ocfs2/inode.c b/fs/ocfs2/inode.c
> index 14bf440ea4df..3feeaa475b62 100644
> --- a/fs/ocfs2/inode.c
> +++ b/fs/ocfs2/inode.c
> @@ -1455,7 +1455,14 @@ int ocfs2_validate_inode_block(struct super_block *sb,
>  		     (unsigned long long)bh->b_blocknr);
>  		goto bail;
>  	}
> -
> +	if (!le16_to_cpu(di->i_links_count) && !le16_to_cpu(di->i_mode) &&
> +		!(le32_to_cpu(di->i_flags) & OCFS2_ORPHANED_FL)) {

	    ^Better to align here.

> +			mlog(ML_ERROR, "Invalid dinode #%llu: "

One tab is engough.

Joseph
> +				"Corrupt state (nlink=0, mode=0, !orphan) detected!\n",
> +			        (unsigned long long)bh->b_blocknr);
> +			rc = -EFSCORRUPTED;
> +			goto bail;
> +	}
>  	/*
>  	 * Errors after here are fatal.
>  	 */

[PATCH v4] ocfs2: Invalidate inode if i_mode is zero after block read

[Ahmet Eray Karadag]

A panic occurs in ocfs2_unlink due to WARN_ON(inode->i_nlink == 0) when
handling a corrupted inode with i_mode=0 and i_nlink=0 in memory.

This "zombie" inode is created because ocfs2_read_locked_inode proceeds
even after ocfs2_validate_inode_block successfully validates a block
that structurally looks okay (passes checksum, signature etc.) but
contains semantically invalid data (specifically i_mode=0). The current
validation function doesn't check for i_mode being zero.

This results in an in-memory inode with i_mode=0 being added to the VFS
cache, which later triggers the panic during unlink.

Prevent this by adding an explicit check for i_mode == 0 within
ocfs2_validate_inode_block. If i_mode is zero, return -EFSCORRUPTED to signal
corruption. This causes the caller (ocfs2_read_locked_inode) to invoke
make_bad_inode(), correctly preventing the zombie inode from entering
the cache.

---
[RFC]:
The current fix handles i_mode=0 corruption detected during inode read
by returning -EFSCORRUPTED from ocfs2_validate_inode_block, which leads to
make_bad_inode() being called, preventing the corrupted inode from
entering the cache. This approach avoids immediately forcing the entire
filesystem read-only, assuming the corruption might be localized to
this inode.

Is this less aggressive error handling strategy appropriate for i_mode=0
corruption? Or is this condition considered severe enough that we *should*
explicitly call ocfs2_error() within the validation function to guarantee
the filesystem is marked read-only immediately upon detection?
Feedback and testing on the correct severity assessment and error
handling for this type of corruption would be appreciated.

Reported-by: syzbot+55c40ae8a0e5f3659f2b@syzkaller.appspotmail.com
Fixes: https://syzkaller.appspot.com/bug?extid=55c40ae8a0e5f3659f2b
Co-developed-by: Albin Babu Varghese <albinbabuvarghese20@gmail.com>
Signed-off-by: Albin Babu Varghese <albinbabuvarghese20@gmail.com>
Signed-off-by: Ahmet Eray Karadag <eraykrdg1@gmail.com>
---
v2:
 - Reviewed how ext4 handling same situation and we come up with this
   solution
---
v3:
 - Implement combined check for nlink=0, mode=0 and non-orphan
   as requested.
---
v4:
 - Fix code alignment issues
---
 fs/ocfs2/inode.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/fs/ocfs2/inode.c b/fs/ocfs2/inode.c
index 14bf440ea4df..d966df3aa605 100644
--- a/fs/ocfs2/inode.c
+++ b/fs/ocfs2/inode.c
@@ -1455,7 +1455,14 @@ int ocfs2_validate_inode_block(struct super_block *sb,
 		     (unsigned long long)bh->b_blocknr);
 		goto bail;
 	}
-
+	if (!le16_to_cpu(di->i_links_count) && !le16_to_cpu(di->i_mode) &&
+		!(le32_to_cpu(di->i_flags) & OCFS2_ORPHANED_FL)) {
+		mlog(ML_ERROR, "Invalid dinode #%llu: "
+			"Corrupt state (nlink=0, mode=0, !orphan) detected!\n",
+		        (unsigned long long)bh->b_blocknr);
+		rc = -EFSCORRUPTED;
+		goto bail;
+	}
 	/*
 	 * Errors after here are fatal.
 	 */
-- 
2.43.0

[PATCH v4] ocfs2: Invalidate inode if i_mode is zero after block read

[Ahmet Eray Karadag]

A panic occurs in ocfs2_unlink due to WARN_ON(inode->i_nlink == 0) when
handling a corrupted inode with i_mode=0 and i_nlink=0 in memory.

This "zombie" inode is created because ocfs2_read_locked_inode proceeds
even after ocfs2_validate_inode_block successfully validates a block
that structurally looks okay (passes checksum, signature etc.) but
contains semantically invalid data (specifically i_mode=0). The current
validation function doesn't check for i_mode being zero.

This results in an in-memory inode with i_mode=0 being added to the VFS
cache, which later triggers the panic during unlink.

Prevent this by adding an explicit check for (i_mode == 0, i_nlink == 0, non-orphan)
within ocfs2_validate_inode_block. If the check is true, return -EFSCORRUPTED to signal
corruption. This causes the caller (ocfs2_read_locked_inode) to invoke
make_bad_inode(), correctly preventing the zombie inode from entering
the cache.

Reported-by: syzbot+55c40ae8a0e5f3659f2b@syzkaller.appspotmail.com
Fixes: https://syzkaller.appspot.com/bug?extid=55c40ae8a0e5f3659f2b
Co-developed-by: Albin Babu Varghese <albinbabuvarghese20@gmail.com>
Signed-off-by: Albin Babu Varghese <albinbabuvarghese20@gmail.com>
Signed-off-by: Ahmet Eray Karadag <eraykrdg1@gmail.com>
Previous link: https://lore.kernel.org/all/20251022222752.46758-2-eraykrdg1@gmail.com/T/
---
v2:
 - Only checking either i_links_count == 0 or i_mode == 0
 - Not performing le16_to_cpu() anymore
 - Tested with ocfs2-test
---
v3:
 - Add checking both high and low bits of i_links_count
---
v4:
 - Reading i_links_count hi and low bits without helper function
  to save few cpu cycles
---
 fs/ocfs2/inode.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/fs/ocfs2/inode.c b/fs/ocfs2/inode.c
index 14bf440ea4df..34c2882273ae 100644
--- a/fs/ocfs2/inode.c
+++ b/fs/ocfs2/inode.c
@@ -1455,7 +1455,13 @@ int ocfs2_validate_inode_block(struct super_block *sb,
 		     (unsigned long long)bh->b_blocknr);
 		goto bail;
 	}
-
+	if (!(di->i_links_count | di->i_links_count_hi) || !di->i_mode) {
+		mlog(ML_ERROR, "Invalid dinode #%llu: "
+			"Corrupt state (nlink=0 or mode=0,) detected!\n",
+		        (unsigned long long)bh->b_blocknr);
+		rc = -EFSCORRUPTED;
+		goto bail;
+	}
 	/*
 	 * Errors after here are fatal.
 	 */
-- 
2.43.0

Re: [PATCH v4] ocfs2: Invalidate inode if i_mode is zero after block read

[Joseph Qi]

On 2025/12/2 08:32, Ahmet Eray Karadag wrote:
> A panic occurs in ocfs2_unlink due to WARN_ON(inode->i_nlink == 0) when
> handling a corrupted inode with i_mode=0 and i_nlink=0 in memory.
> 
> This "zombie" inode is created because ocfs2_read_locked_inode proceeds
> even after ocfs2_validate_inode_block successfully validates a block
> that structurally looks okay (passes checksum, signature etc.) but
> contains semantically invalid data (specifically i_mode=0). The current
> validation function doesn't check for i_mode being zero.
> 
> This results in an in-memory inode with i_mode=0 being added to the VFS
> cache, which later triggers the panic during unlink.
> 
> Prevent this by adding an explicit check for (i_mode == 0, i_nlink == 0, non-orphan)
> within ocfs2_validate_inode_block. If the check is true, return -EFSCORRUPTED to signal
> corruption. This causes the caller (ocfs2_read_locked_inode) to invoke
> make_bad_inode(), correctly preventing the zombie inode from entering
> the cache.
> 
> Reported-by: syzbot+55c40ae8a0e5f3659f2b@syzkaller.appspotmail.com
> Fixes: https://syzkaller.appspot.com/bug?extid=55c40ae8a0e5f3659f2b
> Co-developed-by: Albin Babu Varghese <albinbabuvarghese20@gmail.com>
> Signed-off-by: Albin Babu Varghese <albinbabuvarghese20@gmail.com>
> Signed-off-by: Ahmet Eray Karadag <eraykrdg1@gmail.com>
> Previous link: https://lore.kernel.org/all/20251022222752.46758-2-eraykrdg1@gmail.com/T/
> ---
> v2:
>  - Only checking either i_links_count == 0 or i_mode == 0
>  - Not performing le16_to_cpu() anymore
>  - Tested with ocfs2-test
> ---
> v3:
>  - Add checking both high and low bits of i_links_count
> ---
> v4:
>  - Reading i_links_count hi and low bits without helper function
>   to save few cpu cycles
> ---
>  fs/ocfs2/inode.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/ocfs2/inode.c b/fs/ocfs2/inode.c
> index 14bf440ea4df..34c2882273ae 100644
> --- a/fs/ocfs2/inode.c
> +++ b/fs/ocfs2/inode.c
> @@ -1455,7 +1455,13 @@ int ocfs2_validate_inode_block(struct super_block *sb,
>  		     (unsigned long long)bh->b_blocknr);
>  		goto bail;
>  	}
> -
> +	if (!(di->i_links_count | di->i_links_count_hi) || !di->i_mode) {

"(di->i_links_count | di->i_links_count_hi)" looks meaningless.
So if we don't want to introduce the endian coversion here, how about:

if ((!di->i_links_count && !di->i_links_count_hi) || !di->i_mode) {
	...
}

Heming, what's your opinion?

> +		mlog(ML_ERROR, "Invalid dinode #%llu: "
> +			"Corrupt state (nlink=0 or mode=0,) detected!\n",

Better to log the actual i_nlink/i_mode. e.g.

"corrupted i_nlink %u or i_mode %u\n"
...

Joseph

> +		        (unsigned long long)bh->b_blocknr);
> +		rc = -EFSCORRUPTED;
> +		goto bail;
> +	}
>  	/*
>  	 * Errors after here are fatal.
>  	 */

Re: [PATCH v4] ocfs2: Invalidate inode if i_mode is zero after block read

[Heming Zhao]

On Tue, Dec 02, 2025 at 10:44:21AM +0800, Joseph Qi wrote:
> 
> 
> On 2025/12/2 08:32, Ahmet Eray Karadag wrote:
> > A panic occurs in ocfs2_unlink due to WARN_ON(inode->i_nlink == 0) when
> > handling a corrupted inode with i_mode=0 and i_nlink=0 in memory.
> > 
> > This "zombie" inode is created because ocfs2_read_locked_inode proceeds
> > even after ocfs2_validate_inode_block successfully validates a block
> > that structurally looks okay (passes checksum, signature etc.) but
> > contains semantically invalid data (specifically i_mode=0). The current
> > validation function doesn't check for i_mode being zero.
> > 
> > This results in an in-memory inode with i_mode=0 being added to the VFS
> > cache, which later triggers the panic during unlink.
> > 
> > Prevent this by adding an explicit check for (i_mode == 0, i_nlink == 0, non-orphan)
> > within ocfs2_validate_inode_block. If the check is true, return -EFSCORRUPTED to signal
> > corruption. This causes the caller (ocfs2_read_locked_inode) to invoke
> > make_bad_inode(), correctly preventing the zombie inode from entering
> > the cache.
> > 
> > Reported-by: syzbot+55c40ae8a0e5f3659f2b@syzkaller.appspotmail.com
> > Fixes: https://syzkaller.appspot.com/bug?extid=55c40ae8a0e5f3659f2b
> > Co-developed-by: Albin Babu Varghese <albinbabuvarghese20@gmail.com>
> > Signed-off-by: Albin Babu Varghese <albinbabuvarghese20@gmail.com>
> > Signed-off-by: Ahmet Eray Karadag <eraykrdg1@gmail.com>
> > Previous link: https://lore.kernel.org/all/20251022222752.46758-2-eraykrdg1@gmail.com/T/
> > ---
> > v2:
> >  - Only checking either i_links_count == 0 or i_mode == 0
> >  - Not performing le16_to_cpu() anymore
> >  - Tested with ocfs2-test
> > ---
> > v3:
> >  - Add checking both high and low bits of i_links_count
> > ---
> > v4:
> >  - Reading i_links_count hi and low bits without helper function
> >   to save few cpu cycles
> > ---
> >  fs/ocfs2/inode.c | 8 +++++++-
> >  1 file changed, 7 insertions(+), 1 deletion(-)
> > 
> > diff --git a/fs/ocfs2/inode.c b/fs/ocfs2/inode.c
> > index 14bf440ea4df..34c2882273ae 100644
> > --- a/fs/ocfs2/inode.c
> > +++ b/fs/ocfs2/inode.c
> > @@ -1455,7 +1455,13 @@ int ocfs2_validate_inode_block(struct super_block *sb,
> >  		     (unsigned long long)bh->b_blocknr);
> >  		goto bail;
> >  	}
> > -
> > +	if (!(di->i_links_count | di->i_links_count_hi) || !di->i_mode) {
> 
> "(di->i_links_count | di->i_links_count_hi)" looks meaningless.
> So if we don't want to introduce the endian coversion here, how about:
> 
> if ((!di->i_links_count && !di->i_links_count_hi) || !di->i_mode) {
> 	...
> }
> 
> Heming, what's your opinion?

clearer, looks good to me.

> 
> > +		mlog(ML_ERROR, "Invalid dinode #%llu: "
> > +			"Corrupt state (nlink=0 or mode=0,) detected!\n",
> 
> Better to log the actual i_nlink/i_mode. e.g.
> 
> "corrupted i_nlink %u or i_mode %u\n"
> ...
> 
> Joseph

agree.

- Heming
> 
> > +		        (unsigned long long)bh->b_blocknr);
> > +		rc = -EFSCORRUPTED;
> > +		goto bail;
> > +	}
> >  	/*
> >  	 * Errors after here are fatal.
> >  	 */
>