Re: [PATCH v3 07/11] softmmu/physmem: Never return directories from file_ram_open()

[Peter Xu <peterx@redhat.com>]

On Wed, Aug 23, 2023 at 05:34:07PM +0200, David Hildenbrand wrote:
> open() does not fail on directories when opening them readonly (O_RDONLY).
> 
> Currently, we succeed opening such directories and fail later during
> mmap(), resulting in a misleading error message.
> 
> $ ./qemu-system-x86_64 \
>     -object memory-backend-file,id=ram0,mem-path=tmp,readonly=true,size=1g
>  qemu-system-x86_64: unable to map backing store for guest RAM: No such device
> 
> To identify directories and handle them accordingly in file_ram_open()
> also when readonly=true was specified, detect if we just opened a directory
> using fstat() instead. Then, fail file_ram_open() right away, similarly
> to how we now fail if the file does not exist and we want to open the
> file readonly.
> 
> With this change, we get a nicer error message:
>  qemu-system-x86_64: can't open backing store tmp for guest RAM: Is a directory
> 
> Note that the only memory-backend-file will end up calling
> memory_region_init_ram_from_file() -> qemu_ram_alloc_from_file() ->
> file_ram_open().
> 
> Reported-by: Thiner Logoer <logoerthiner1@163.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>

Reviewed-by: Peter Xu <peterx@redhat.com>

-- 
Peter Xu