Hello David,
+-- On Mon, 25 Mar 2019, David Gibson wrote --+
| The only inherent limit to dtb size should be 2^31-1 bytes (the format
| uses signed 32-bit ints as offsets).
~2GB of dtb?! Seems quite big to specify the h/w that a kernel is
going to run/boot on.
| Indeed there shouldn't be any architecture (as in instruction set)
| dependent limits either. There may however be more specific platform
| dependent limits.
$ find . -name \*.dts -exec ls -shXS --color {} \; | sort -grk1 | less -r
-> https://paste.fedoraproject.org/paste/~9p-lVWwX7jmngHMQjCBsg
Going through the .dts files in the Linux kernel tree, 64KB appears to top
the list of file sizes.
IMO, generic 2MB of dtb size limit is reasonable; Considering 64KB is the max
we are seeing, plus QEMU has FDT_MAX_SIZE defined to be 0x100000(~1MB), and
noone has complained that it's too small.
| Yeah, you should probably make that hard error rather than truncating.
| If a system works with a truncated tree, it can only be by sheer
| accident.
Yes, current patch would 'goto fail; if (dt_size > FDT_MAX_SIZE)'.
Thank you.
--
Prasad J Pandit / Red Hat Product Security Team
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