[LEDE-DEV] Update to util-linux 2.30.1 breaks x86_64 squashfs-combined

[Felix Fietkau]

On 2017-09-29 13:04, Daniel Golle wrote:
> On Fri, Sep 29, 2017 at 12:20:08PM +0200, Felix Fietkau wrote:
>> On 2017-09-11 02:33, Philip Prindeville wrote:
>> > Changing the subject from the previous thread as it turned out to not have to do with sysupgrade at all.
>> > 
>> > What I can tell is this, having added some tracing to fstools.
>> > 
>> > We get to the call to system() in rootdisk_volume_init():
>> > 
>> > https://git.lede-project.org/?p=project/fstools.git;a=blob;f=libfstools/rootdisk.c;h=dd00c1b4e5b4aa9b748610fa3e93d301a67101a7;hb=HEAD#l269
>> > 
>> > and it never seems to return.  The value of “str” is “mkfs.f2fs -q -l rootfs_data /dev/loop0”.
>> > 
>> > What would cause this to hang rather than return an error?
>> I've used sysrq to trace this and found out that it's hanging in the
>> getrandom system call, which could be used through util-linux library
>> code. That also explains why the update broke it.
>> 
>> I will prepare a patch that forces util-linux to stick to /dev/urandom
>> instead - that should hopefully fix this for good.
> 
> mkfs.f2fs also uses getrandom(3) and hangs there for some minutes when
> creating the initial snapshot...
I don't see any direct calls to getrandom from mkfs.f2fs, so I assume
they are issued through util-linux libuuid. That would explain why my
change fixes the issue (with f2fs as overlay fs) for me, and results in
the following new warning:

[    8.756017] random: mkfs.f2fs: uninitialized urandom read (16 bytes read)

- Felix