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Squashfs: check the inode number is not the invalid value of zero

Brian Foster requested to merge bfoster2/centos-stream-9:jira35098-squashfs-ino-not-zero into main

JIRA: https://issues.redhat.com/browse/RHEL-35098
Upstream Status: linux.git
CVE: CVE-2024-26982

commit 9253c54e01b6505d348afbc02abaa4d9f8a01395
Author: Phillip Lougher phillip@squashfs.org.uk
Date: Mon Apr 8 23:02:06 2024 +0100

Squashfs: check the inode number is not the invalid value of zero  

Syskiller has produced an out of bounds access in fill_meta_index().  

That out of bounds access is ultimately caused because the inode  
has an inode number with the invalid value of zero, which was not checked.  

The reason this causes the out of bounds access is due to following  
sequence of events:  

1. Fill_meta_index() is called to allocate (via empty_meta_index())  
   and fill a metadata index.  It however suffers a data read error  
   and aborts, invalidating the newly returned empty metadata index.  
   It does this by setting the inode number of the index to zero,  
   which means unused (zero is not a valid inode number).  

2. When fill_meta_index() is subsequently called again on another  
   read operation, locate_meta_index() returns the previous index  
   because it matches the inode number of 0.  Because this index  
   has been returned it is expected to have been filled, and because  
   it hasn't been, an out of bounds access is performed.  

This patch adds a sanity check which checks that the inode number  
is not zero when the inode is created and returns -EINVAL if it is.  

[phillip@squashfs.org.uk: whitespace fix]  
  Link: https://lkml.kernel.org/r/20240409204723.446925-1-phillip@squashfs.org.uk  
Link: https://lkml.kernel.org/r/20240408220206.435788-1-phillip@squashfs.org.uk  
Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>  
Reported-by: "Ubisectech Sirius" <bugreport@ubisectech.com>  
Closes: https://lore.kernel.org/lkml/87f5c007-b8a5-41ae-8b57-431e924c5915.bugreport@ubisectech.com/  
Cc: Christian Brauner <brauner@kernel.org>  
Cc: <stable@vger.kernel.org>  
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Signed-off-by: Brian Foster bfoster@redhat.com

Edited by Brian Foster

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