There are multiple similar bugs implicitly introduced by the
commit c0cfa2d8a788fcf4 ("vsock: add multi-transports support") and
commit 6a2c0962105ae8ce ("vsock: prevent transport modules unloading").
The bug pattern:
[1] vsock_sock.transport pointer is copied to a local variable,
[2] lock_sock() is called,
[3] the local variable is used.
VSOCK multi-transport support introduced the race condition:
vsock_sock.transport value may change between [1] and [2].
Let's copy vsock_sock.transport pointer to local variables after
the lock_sock() call.
Multiple CPUs may be mapped to the same hctx, allowing mulitple
submission contexts to attempt commit_rqs(). We need to verify we're
not writing the same doorbell value multiple times since that's a spec
violation.
UBUNTU: SAUCE: lib/decompress_unlz4.c: correctly handle zero-padding around initrds.
lz4 compatible decompressor is simple. The format is underspecified
and relies on EOF notification to determine when to stop. Initramfs
buffer format[1] explicitely states that it can have arbitrary number
of zero padding. Thus when operating without a fill function, be extra
careful to ensure that sizes less than 4, or apperantly empty
chunksizes are treated as EOF.
To test this I have created two cpio initrds, first a normal one,
main.cpio. And second one with just a single /test-file with content
"second" second.cpio. Then i compressed both of them with gzip, and
with lz4 -l. Then I created a padding of 4 bytes (dd if=/dev/zero
of=pad4 bs=1 count=4). To create four testcase initrds:
The pad4 test-cases replicate the initrd load by grub, as it pads and
aligns every initrd it loads.
All of the above boot, however /test-file was not accessible in the
initrd for the testcase #4, as decoding in lz4 decompressor
failed. Also an error message printed which usually is harmless.
Whith a patched kernel, all of the above testcases now pass, and
/test-file is accessible.
This fixes lz4 initrd decompress warning on every boot with grub. And
more importantly this fixes inability to load multiple lz4 compressed
initrds with grub.
I guess I should convert above decompressor streams with/without
padding into kunit tests, across all decompressor algorithms.
