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43fb2b30ee
Before the cited commit, the kernel unconditionally embedded SCM
credentials to skb for embryo sockets even when both the sender
and listener disabled SO_PASSCRED and SO_PASSPIDFD.
Now, the credentials are added to skb only when configured by the
sender or the listener.
However, as reported in the link below, it caused a regression for
some programs that assume credentials are included in every skb,
but sometimes not now.
The only problematic scenario would be that a socket starts listening
before setting the option. Then, there will be 2 types of non-small
race window, where a client can send skb without credentials, which
the peer receives as an "invalid" message (and aborts the connection
it seems ?):
Client Server
------ ------
s1.listen() <-- No SO_PASS{CRED,PIDFD}
s2.connect()
s2.send() <-- w/o cred
s1.setsockopt(SO_PASS{CRED,PIDFD})
s2.send() <-- w/ cred
or
Client Server
------ ------
s1.listen() <-- No SO_PASS{CRED,PIDFD}
s2.connect()
s2.send() <-- w/o cred
s3, _ = s1.accept() <-- Inherit cred options
s2.send() <-- w/o cred but not set yet
s3.setsockopt(SO_PASS{CRED,PIDFD})
s2.send() <-- w/ cred
It's unfortunate that buggy programs depend on the behaviour,
but let's restore the previous behaviour.
Fixes:
|
||
|---|---|---|
| .. | ||
| af_unix.c | ||
| af_unix.h | ||
| diag.c | ||
| garbage.c | ||
| Kconfig | ||
| Makefile | ||
| sysctl_net_unix.c | ||
| unix_bpf.c | ||