https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=253500
Bug ID: 253500
Summary: fusefs: F_SETLKW fcntl gets corrupted by kern_fcntl()
Product: Base System
Version: 12.2-RELEASE
Hardware: Any
OS: Any
Status: New
Severity: Affects Only Me
Priority: ---
Component: kern
Assignee: [email protected]
Reporter: [email protected]
Created attachment 222425
--> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=222425&action=edit
quick-n-dirty patch to fix fcntl locking in FUSE
There's at least two bugs in fcntl lock handling that get tickled by FUSE:
1. Calls to `fcntl(fd, F_SETLKW, &lock)` are showing up in the FUSE server as
a FUSE_SETLK (should be FUSE_SETLKW).
2. fcntl calls to _clear_ a lock, by using F_SETLK with `l_type = F_UNLCK`,
never get passed to userspace at all.
It looks like both incorrect behaviors are caused by `kern_fcntl()`:
* F_SETLKW is handled by a switch-case fallthrough to the F_SETLK path, but
the
`VOP_ADVLOCK()' call is hardcoded to use `F_SETLK'.
* In the nested switch over the lock type, several calls to `VOP_ADVLOCK()'
are
performed using the lock type (e.g. `F_UNLCK') where they should use the
fcntl
opcode. This causes `fuse_vnop_advlock()' to return EINVAL.
Attached is a patch that fixes both issues according to my test suite. I'm not
very familiar with the FreeBSD kernel, so note that this patch might not do the
right thing for other filesystem drivers.
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