netfs, 9p: Fix race between umount and async request completion There's a problem in 9p's interaction with netfslib whereby a crash occurs because the 9p_fid structs get forcibly destroyed during client teardown (without paying attention to their refcounts) before netfslib has finished with them. However, it's not a simple case of deferring the clunking that p9_fid_put() does as that requires the p9_client record to still be present. The problem is that netfslib has to unlock pages and clear the IN_PROGRESS flag before destroying the objects involved - including the fid - and, in any case, nothing checks to see if writeback completed barring looking at the page flags. Fix this by keeping a count of outstanding I/O requests (of any type) and waiting for it to quiesce during inode eviction. Reported-by: syzbot+df038d463cca332e8414@xxxxxxxxxxxxxxxxxxxxxxxxx Link: https://lore.kernel.org/all/0000000000005be0aa061846f8d6@xxxxxxxxxx/ Reported-by: syzbot+d7c7a495a5e466c031b6@xxxxxxxxxxxxxxxxxxxxxxxxx Link: https://lore.kernel.org/all/000000000000b86c5e06130da9c6@xxxxxxxxxx/ Reported-by: syzbot+1527696d41a634cc1819@xxxxxxxxxxxxxxxxxxxxxxxxx Link: https://lore.kernel.org/all/000000000000041f960618206d7e@xxxxxxxxxx/ Signed-off-by: David Howells <dhowells@xxxxxxxxxx> Reviewed-by: Dominique Martinet <asmadeus@xxxxxxxxxxxxx> Tested-by: syzbot+d7c7a495a5e466c031b6@xxxxxxxxxxxxxxxxxxxxxxxxx cc: Eric Van Hensbergen <ericvh@xxxxxxxxxx> cc: Latchesar Ionkov <lucho@xxxxxxxxxx> cc: Christian Schoenebeck <linux_oss@xxxxxxxxxxxxx> cc: Jeff Layton <jlayton@xxxxxxxxxx> cc: Steve French <sfrench@xxxxxxxxx> cc: Hillf Danton <hdanton@xxxxxxxx> cc: v9fs@xxxxxxxxxxxxxxx cc: linux-afs@xxxxxxxxxxxxxxxxxxx cc: linux-cifs@xxxxxxxxxxxxxxx cc: netfs@xxxxxxxxxxxxxxx cc: linux-fsdevel@xxxxxxxxxxxxxxx --- Notes: Changes ======= ver #3) - Adjust commit message; no change to the diff. ver #2) - Wait for outstanding I/O before clobbering the pagecache. fs/9p/vfs_inode.c | 1 + fs/afs/inode.c | 1 + fs/netfs/objects.c | 5 +++++ fs/smb/client/cifsfs.c | 1 + include/linux/netfs.h | 18 ++++++++++++++++++ 5 files changed, 26 insertions(+) diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c index 8c9a896d691e..effb3aa1f3ed 100644 --- a/fs/9p/vfs_inode.c +++ b/fs/9p/vfs_inode.c @@ -349,6 +349,7 @@ void v9fs_evict_inode(struct inode *inode) __le32 __maybe_unused version; if (!is_bad_inode(inode)) { + netfs_wait_for_outstanding_io(inode); truncate_inode_pages_final(&inode->i_data); version = cpu_to_le32(v9inode->qid.version); diff --git a/fs/afs/inode.c b/fs/afs/inode.c index 94fc049aff58..15bb7989c387 100644 --- a/fs/afs/inode.c +++ b/fs/afs/inode.c @@ -648,6 +648,7 @@ void afs_evict_inode(struct inode *inode) ASSERTCMP(inode->i_ino, ==, vnode->fid.vnode); + netfs_wait_for_outstanding_io(inode); truncate_inode_pages_final(&inode->i_data); afs_set_cache_aux(vnode, &aux); diff --git a/fs/netfs/objects.c b/fs/netfs/objects.c index c90d482b1650..f4a642727479 100644 --- a/fs/netfs/objects.c +++ b/fs/netfs/objects.c @@ -72,6 +72,7 @@ struct netfs_io_request *netfs_alloc_request(struct address_space *mapping, } } + atomic_inc(&ctx->io_count); trace_netfs_rreq_ref(rreq->debug_id, 1, netfs_rreq_trace_new); netfs_proc_add_rreq(rreq); netfs_stat(&netfs_n_rh_rreq); @@ -124,6 +125,7 @@ static void netfs_free_request(struct work_struct *work) { struct netfs_io_request *rreq = container_of(work, struct netfs_io_request, work); + struct netfs_inode *ictx = netfs_inode(rreq->inode); unsigned int i; trace_netfs_rreq(rreq, netfs_rreq_trace_free); @@ -142,6 +144,9 @@ static void netfs_free_request(struct work_struct *work) } kvfree(rreq->direct_bv); } + + if (atomic_dec_and_test(&ictx->io_count)) + wake_up_var(&ictx->io_count); call_rcu(&rreq->rcu, netfs_free_request_rcu); } diff --git a/fs/smb/client/cifsfs.c b/fs/smb/client/cifsfs.c index ec5b639f421a..14810ffd15c8 100644 --- a/fs/smb/client/cifsfs.c +++ b/fs/smb/client/cifsfs.c @@ -431,6 +431,7 @@ cifs_free_inode(struct inode *inode) static void cifs_evict_inode(struct inode *inode) { + netfs_wait_for_outstanding_io(inode); truncate_inode_pages_final(&inode->i_data); if (inode->i_state & I_PINNING_NETFS_WB) cifs_fscache_unuse_inode_cookie(inode, true); diff --git a/include/linux/netfs.h b/include/linux/netfs.h index d2d291a9cdad..3ca3906bb8da 100644 --- a/include/linux/netfs.h +++ b/include/linux/netfs.h @@ -68,6 +68,7 @@ struct netfs_inode { loff_t remote_i_size; /* Size of the remote file */ loff_t zero_point; /* Size after which we assume there's no data * on the server */ + atomic_t io_count; /* Number of outstanding reqs */ unsigned long flags; #define NETFS_ICTX_ODIRECT 0 /* The file has DIO in progress */ #define NETFS_ICTX_UNBUFFERED 1 /* I/O should not use the pagecache */ @@ -474,6 +475,7 @@ static inline void netfs_inode_init(struct netfs_inode *ctx, ctx->remote_i_size = i_size_read(&ctx->inode); ctx->zero_point = LLONG_MAX; ctx->flags = 0; + atomic_set(&ctx->io_count, 0); #if IS_ENABLED(CONFIG_FSCACHE) ctx->cache = NULL; #endif @@ -517,4 +519,20 @@ static inline struct fscache_cookie *netfs_i_cookie(struct netfs_inode *ctx) #endif } +/** + * netfs_wait_for_outstanding_io - Wait for outstanding I/O to complete + * @ctx: The netfs inode to wait on + * + * Wait for outstanding I/O requests of any type to complete. This is intended + * to be called from inode eviction routines. This makes sure that any + * resources held by those requests are cleaned up before we let the inode get + * cleaned up. + */ +static inline void netfs_wait_for_outstanding_io(struct inode *inode) +{ + struct netfs_inode *ictx = netfs_inode(inode); + + wait_var_event(&ictx->io_count, atomic_read(&ictx->io_count) == 0); +} + #endif /* _LINUX_NETFS_H */
