Re: [BUG] commit fails with 'bus error' when working directory is on an NFS share
- From
Jeff King <peff@peff.net>
- Date
- Dec 5, 2024, 03:22 UTC
- Message-ID
- <20241205032246.GA2573761@coredump.intra.peff.net>
- In-Reply-To
- <CAJ-DG_AU8cFdLqfAnEE8N2KSqnQgJ47YJszyXWOvXuuKreAbCw@mail.gmail.com>
On Wed, Dec 04, 2024 at 07:21:16PM -0700, Dmitriy Panteleyev wrote:
> NFS server is on a linux bot on LAN. nfs-kernel-server 2.6.1. Client > mounts shares as vers=3.
My setup was a little different, but I tried the same thing doing an actual cross-network mount of an older box with 2.6.2, and making sure to use vers=3. Still can't reproduce.
> After trying NO_MMAP=1 with and without SANITIZE, I get: > "fatal: mmap failed: Permission denied"
Hmm, that's odd. If you run it under strace, which syscall fails? That message should be reporting errno from mmap(), which in NO_MMAP mode should be a pread() call. I'm not sure why that would get EACCES if the open() call succeeded, but that might explain why the mmap'd version gets SIGBUS (I don't know much about NFS, but I imagine that under the hood the client is probably issuing reads for individual pages to fault in the map).
Does your system have AppArmor enabled?
This issue sounds similar to yours:
https://unix.stackexchange.com/questions/633389/man-cannot-read-manpage-from-nfs-although-the-file-is-readable
especially the bit where reading the metadata once makes it magically work for a brief period (which is the only thing I'd expect the commit you found via bisection to have an effect on).
-Peff