Re: [PATCH] adfs: validate nzones in adfs_read_map()

[Russell King (Oracle)]

On Fri, Mar 20, 2026 at 03:23:56PM +0100, Greg Kroah-Hartman wrote:
> From: Bae Yeonju <iwasbaeyz@xxxxxxxxx>
> 
> adfs_read_map() reads the zone count from the on-disk disc record
> without validation:
> 
>   nzones = dr->nzones | dr->nzones_high << 8;
> 
> When nzones is 0, the subsequent kmalloc_array(0, ...) returns
> ZERO_SIZE_PTR (0x10), and adfs_map_layout() writes to dm[-1],
> causing an out-of-bounds write before the allocated buffer.
> 
> This can be triggered by mounting a crafted ADFS filesystem image
> with nzones set to 0 in the disc record. It leads to kernel heap
> corruption and a NULL pointer dereference during mount.
> 
> Add a check to reject disc records with nzones == 0 before the
> allocation.
> 
> Found by syzkaller.

I didn't see this patch.

This is a silly place to put the check - it should be done while
validating the disc record, in adfs_validate_bblk(), not when trying
to use it.

Note that adfs_validate_dr0() already validates the number of zones.

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