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virtiofsd: prevent FUSE_INIT/FUSE_DESTROY races 

When running with multiple threads it can be tricky to handle
FUSE_INIT/FUSE_DESTROY in parallel with other request types or in
parallel with themselves.  Serialize FUSE_INIT and FUSE_DESTROY so that
malicious clients cannot trigger race conditions.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2019-08-01 17:54:07 +01:00 committed by Dr. David Alan Gilbert
parent a3d756c5ae
commit cdc497c692
2 changed files with 19 additions and 0 deletions
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1
tools/virtiofsd/fuse_i.h
View File

@ -61,6 +61,7 @@ struct fuse_session {
struct fuse_req list;
struct fuse_req interrupts;
pthread_mutex_t lock;
pthread_rwlock_t init_rwlock;
int got_destroy;
int broken_splice_nonblock;
uint64_t notify_ctr;

18
tools/virtiofsd/fuse_lowlevel.c
View File

@ -2428,6 +2428,19 @@ void fuse_session_process_buf_int(struct fuse_session *se,
req->ctx.pid = in->pid;
req->ch = ch;
/*
* INIT and DESTROY requests are serialized, all other request types
* run in parallel. This prevents races between FUSE_INIT and ordinary
* requests, FUSE_INIT and FUSE_INIT, FUSE_INIT and FUSE_DESTROY, and
* FUSE_DESTROY and FUSE_DESTROY.
*/
if (in->opcode == FUSE_INIT || in->opcode == CUSE_INIT ||
in->opcode == FUSE_DESTROY) {
pthread_rwlock_wrlock(&se->init_rwlock);
} else {
pthread_rwlock_rdlock(&se->init_rwlock);
}
err = EIO;
if (!se->got_init) {
enum fuse_opcode expected;
@ -2485,10 +2498,13 @@ void fuse_session_process_buf_int(struct fuse_session *se,
} else {
fuse_ll_ops[in->opcode].func(req, in->nodeid, &iter);
}
pthread_rwlock_unlock(&se->init_rwlock);
return;
reply_err:
fuse_reply_err(req, err);
pthread_rwlock_unlock(&se->init_rwlock);
}
#define LL_OPTION(n, o, v) \
@ -2531,6 +2547,7 @@ void fuse_session_destroy(struct fuse_session *se)
se->op.destroy(se->userdata);
}
}
pthread_rwlock_destroy(&se->init_rwlock);
pthread_mutex_destroy(&se->lock);
free(se->cuse_data);
if (se->fd != -1) {
@ -2610,6 +2627,7 @@ struct fuse_session *fuse_session_new(struct fuse_args *args,
list_init_req(&se->list);
list_init_req(&se->interrupts);
fuse_mutex_init(&se->lock);
pthread_rwlock_init(&se->init_rwlock, NULL);
memcpy(&se->op, op, op_size);
se->owner = getuid();