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VOPs like VOP_SETATTR can change a file's size, with the vnode
exclusively locked. But VOPs like VOP_LOOKUP look up the file size from
the server without the vnode locked. So a race is possible. For
example:
1) One thread calls VOP_SETATTR to truncate a file. It locks the vnode
and sends FUSE_SETATTR to the server.
2) A second thread calls VOP_LOOKUP and fetches the file's attributes from
the server. Then it blocks trying to acquire the vnode lock.
3) FUSE_SETATTR returns and the first thread releases the vnode lock.
4) The second thread acquires the vnode lock and caches the file's
attributes, which are now out-of-date.
Fix this race by recording a timestamp in the vnode of the last time
that its filesize was modified. Check that timestamp during VOP_LOOKUP
and VFS_VGET. If it's newer than the time at which FUSE_LOOKUP was
issued to the server, ignore the attributes returned by FUSE_LOOKUP.
PR: 259071
Reported by: Agata <chogata@moosefs.pro>
Reviewed by: pfg
Differential Revision: https://reviews.freebsd.org/D33158
(cherry picked from commit
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| acl | ||
| aio | ||
| audit | ||
| auditpipe | ||
| capsicum | ||
| cddl | ||
| common | ||
| devrandom | ||
| fifo | ||
| file | ||
| fs | ||
| geom | ||
| kern | ||
| kqueue | ||
| mac | ||
| mqueue | ||
| net | ||
| netgraph | ||
| netinet | ||
| netinet6 | ||
| netipsec | ||
| netmap | ||
| netpfil | ||
| opencrypto | ||
| pjdfstest | ||
| posixshm | ||
| sys | ||
| vfs | ||
| vm | ||
| vmm | ||
| Makefile | ||
| Makefile.depend | ||
| Makefile.inc | ||