CVE-2024-26982

In the Linux kernel, the following vulnerability has been resolved:

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.

[[email protected]: whitespace fix]