The following commit has been merged in the openafs-stable-1_8_x branch:
commit 08a90850fd792718ec5abdda172ab0214abfced6
Author: Andrew Deason <[email protected]>
Date: Tue Feb 7 22:48:23 2023 -0600
vol: Re-evaluate conditons for cond vars
Most users of cond vars follow this general pattern when waiting for a
condition:
while (!condition) {
CV_WAIT(cv, mutex);
}
But a few places in src/vol do this:
if (!condition) {
CV_WAIT(cv, mutex);
}
It is important to always re-check for the relevant condition after
waiting for a CV, even if it seems like we only need to wait exactly
once, because pthread_cond_wait() is allowed to wake up its caller
spuriously even the CV hasn't been signalled. On Solaris, this can
actually happen if the calling thread is interrupted by a signal.
In VInitPreAttachVolumes() for DAFS, currently this can cause a
segfault if CV_WAIT returns while 'vq' is empty. We will try to
queue_Remove() the head of the queue itself, resulting in vq.head.next
being set to NULL, which will segfault when we try to pull the next
item off of the queue.
We generally cannot be interrupted by a signal when using opr's
softsig, because signals are only delivered to the softsig thread and
blocked in all other threads. It is technically possible to trigger
this situation on Solaris by sending the (unblockable) SIGCANCEL
signal, though this would be very unusual.
To make sure issues like this cannot happen and to avoid weird corner
cases, adjust all of our CV waiters to wait for a CV using a while()
loop or similar pattern. Spurious wakeups may be impossible with LWP,
but just try to make all code use a similar structure to be safe.
Thanks for [email protected] for finding and investigating the
relevant issue.
Reviewed-on: https://gerrit.openafs.org/15327
Reviewed-by: Cheyenne Wills <[email protected]>
Reviewed-by: Mark Vitale <[email protected]>
Reviewed-by: Marcio Brito Barbosa <[email protected]>
Reviewed-by: Michael Meffie <[email protected]>
Reviewed-by: Benjamin Kaduk <[email protected]>
Tested-by: BuildBot <[email protected]>
(cherry picked from commit 9bc06a059121207b354fdf97f65029d8c2b3df30)
Change-Id: Ib1fdf06570e441b4a322a1e9b90ff084e07ad1fb
Reviewed-on: https://gerrit.openafs.org/15543
Reviewed-by: Andrew Deason <[email protected]>
Tested-by: BuildBot <[email protected]>
Reviewed-by: Marcio Brito Barbosa <[email protected]>
Reviewed-by: Kailas Zadbuke <[email protected]>
Reviewed-by: Stephan Wiesand <[email protected]>
src/vol/volume.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
--
OpenAFS Master Repository
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