From 21f621741a770c119e7529a3f5c0e6b7c91383a3 Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Tue, 6 Jan 2015 10:45:35 +0100 Subject: fuse: fix LOOKUP vs INIT compat handling Analysis from Marc: "Commit 7078187a795f ("fuse: introduce fuse_simple_request() helper") from the above pull request triggers some EIO errors for me in some tests that rely on fuse Looking at the code changes and a bit of debugging info I think there's a general problem here that fuse_get_req checks and possibly waits for fc->initialized, and this was always called first. But this commit changes the ordering and in many places fc->minor is now possibly used before fuse_get_req, and we can't be sure that fc has been initialized. In my case fuse_lookup_init sets req->out.args[0].size to the wrong size because fc->minor at that point is still 0, leading to the EIO error." Fix by moving the compat adjustments into fuse_simple_request() to after fuse_get_req(). This is also more readable than the original, since now compatibility is handled in a single function instead of cluttering each operation. Reported-by: Marc Dionne Tested-by: Marc Dionne Signed-off-by: Miklos Szeredi Fixes: 7078187a795f ("fuse: introduce fuse_simple_request() helper") --- fs/fuse/dev.c | 36 ++++++++++++++++++++++++++++++++++++ 1 file changed, 36 insertions(+) (limited to 'fs/fuse/dev.c') diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index ba1107977f2e..c847d6b225e2 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -511,6 +511,39 @@ void fuse_request_send(struct fuse_conn *fc, struct fuse_req *req) } EXPORT_SYMBOL_GPL(fuse_request_send); +static void fuse_adjust_compat(struct fuse_conn *fc, struct fuse_args *args) +{ + if (fc->minor < 4 && args->in.h.opcode == FUSE_STATFS) + args->out.args[0].size = FUSE_COMPAT_STATFS_SIZE; + + if (fc->minor < 9) { + switch (args->in.h.opcode) { + case FUSE_LOOKUP: + case FUSE_CREATE: + case FUSE_MKNOD: + case FUSE_MKDIR: + case FUSE_SYMLINK: + case FUSE_LINK: + args->out.args[0].size = FUSE_COMPAT_ENTRY_OUT_SIZE; + break; + case FUSE_GETATTR: + case FUSE_SETATTR: + args->out.args[0].size = FUSE_COMPAT_ATTR_OUT_SIZE; + break; + } + } + if (fc->minor < 12) { + switch (args->in.h.opcode) { + case FUSE_CREATE: + args->in.args[0].size = sizeof(struct fuse_open_in); + break; + case FUSE_MKNOD: + args->in.args[0].size = FUSE_COMPAT_MKNOD_IN_SIZE; + break; + } + } +} + ssize_t fuse_simple_request(struct fuse_conn *fc, struct fuse_args *args) { struct fuse_req *req; @@ -520,6 +553,9 @@ ssize_t fuse_simple_request(struct fuse_conn *fc, struct fuse_args *args) if (IS_ERR(req)) return PTR_ERR(req); + /* Needs to be done after fuse_get_req() so that fc->minor is valid */ + fuse_adjust_compat(fc, args); + req->in.h.opcode = args->in.h.opcode; req->in.h.nodeid = args->in.h.nodeid; req->in.numargs = args->in.numargs; -- cgit v1.2.3 From 9759bd51899458af4f4bcc11046f01285642ca10 Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Tue, 6 Jan 2015 10:45:35 +0100 Subject: fuse: add memory barrier to INIT Theoretically we need to order setting of various fields in fc with fc->initialized. No known bug reports related to this yet. Signed-off-by: Miklos Szeredi --- fs/fuse/dev.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) (limited to 'fs/fuse/dev.c') diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index c847d6b225e2..ed19a7d622fa 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -131,6 +131,13 @@ static void fuse_req_init_context(struct fuse_req *req) req->in.h.pid = current->pid; } +void fuse_set_initialized(struct fuse_conn *fc) +{ + /* Make sure stores before this are seen on another CPU */ + smp_wmb(); + fc->initialized = 1; +} + static bool fuse_block_alloc(struct fuse_conn *fc, bool for_background) { return !fc->initialized || (for_background && fc->blocked); @@ -155,6 +162,8 @@ static struct fuse_req *__fuse_get_req(struct fuse_conn *fc, unsigned npages, if (intr) goto out; } + /* Matches smp_wmb() in fuse_set_initialized() */ + smp_rmb(); err = -ENOTCONN; if (!fc->connected) @@ -253,6 +262,8 @@ struct fuse_req *fuse_get_req_nofail_nopages(struct fuse_conn *fc, atomic_inc(&fc->num_waiting); wait_event(fc->blocked_waitq, fc->initialized); + /* Matches smp_wmb() in fuse_set_initialized() */ + smp_rmb(); req = fuse_request_alloc(0); if (!req) req = get_reserved_req(fc, file); @@ -2163,7 +2174,7 @@ void fuse_abort_conn(struct fuse_conn *fc) if (fc->connected) { fc->connected = 0; fc->blocked = 0; - fc->initialized = 1; + fuse_set_initialized(fc); end_io_requests(fc); end_queued_requests(fc); end_polls(fc); @@ -2182,7 +2193,7 @@ int fuse_dev_release(struct inode *inode, struct file *file) spin_lock(&fc->lock); fc->connected = 0; fc->blocked = 0; - fc->initialized = 1; + fuse_set_initialized(fc); end_queued_requests(fc); end_polls(fc); wake_up_all(&fc->blocked_waitq); -- cgit v1.2.3