From 1644ccc8a99ae73859c39372f96afdbf03c9f80d Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sat, 18 Apr 2009 02:32:31 -0400 Subject: Safer nfsd_cross_mnt() AFAICS, we have a subtle bug there: if we have crossed mountpoint *and* it got mount --move'd away, we'll be holding only one reference to fs containing dentry - exp->ex_path.mnt. IOW, we ought to dput() before exp_put(). Signed-off-by: Al Viro --- fs/nfsd/vfs.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) (limited to 'fs/nfsd/vfs.c') diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c index ab93fcfef254..46e6bd2d4f07 100644 --- a/fs/nfsd/vfs.c +++ b/fs/nfsd/vfs.c @@ -116,10 +116,15 @@ nfsd_cross_mnt(struct svc_rqst *rqstp, struct dentry **dpp, } if ((exp->ex_flags & NFSEXP_CROSSMOUNT) || EX_NOHIDE(exp2)) { /* successfully crossed mount point */ - exp_put(exp); - *expp = exp2; + /* + * This is subtle: dentry is *not* under mnt at this point. + * The only reason we are safe is that original mnt is pinned + * down by exp, so we should dput before putting exp. + */ dput(dentry); *dpp = mounts; + exp_put(exp); + *expp = exp2; } else { exp_put(exp2); dput(mounts); -- cgit v1.2.1 From 2f9092e1020246168b1309b35e085ecd7ff9ff72 Mon Sep 17 00:00:00 2001 From: David Woodhouse Date: Mon, 20 Apr 2009 23:18:37 +0100 Subject: Fix i_mutex vs. readdir handling in nfsd Commit 14f7dd63 ("Copy XFS readdir hack into nfsd code") introduced a bug to generic code which had been extant for a long time in the XFS version -- it started to call through into lookup_one_len() and hence into the file systems' ->lookup() methods without i_mutex held on the directory. This patch fixes it by locking the directory's i_mutex again before calling the filldir functions. The original deadlocks which commit 14f7dd63 was designed to avoid are still avoided, because they were due to fs-internal locking, not i_mutex. While we're at it, fix the return type of nfsd_buffered_readdir() which should be a __be32 not an int -- it's an NFS errno, not a Linux errno. And return nfserrno(-ENOMEM) when allocation fails, not just -ENOMEM. Sparse would have caught that, if it wasn't so busy bitching about __cold__. Commit 05f4f678 ("nfsd4: don't do lookup within readdir in recovery code") introduced a similar problem with calling lookup_one_len() without i_mutex, which this patch also addresses. To fix that, it was necessary to fix the called functions so that they expect i_mutex to be held; that part was done by J. Bruce Fields. Signed-off-by: David Woodhouse Umm-I-can-live-with-that-by: Al Viro Reported-by: J. R. Okajima Tested-by: J. Bruce Fields LKML-Reference: <8036.1237474444@jrobl> Cc: stable@kernel.org Signed-off-by: Al Viro --- fs/nfsd/vfs.c | 25 +++++++++++++++++++------ 1 file changed, 19 insertions(+), 6 deletions(-) (limited to 'fs/nfsd/vfs.c') diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c index 46e6bd2d4f07..6c68ffd6b4bb 100644 --- a/fs/nfsd/vfs.c +++ b/fs/nfsd/vfs.c @@ -1890,8 +1890,8 @@ static int nfsd_buffered_filldir(void *__buf, const char *name, int namlen, return 0; } -static int nfsd_buffered_readdir(struct file *file, filldir_t func, - struct readdir_cd *cdp, loff_t *offsetp) +static __be32 nfsd_buffered_readdir(struct file *file, filldir_t func, + struct readdir_cd *cdp, loff_t *offsetp) { struct readdir_data buf; struct buffered_dirent *de; @@ -1901,11 +1901,12 @@ static int nfsd_buffered_readdir(struct file *file, filldir_t func, buf.dirent = (void *)__get_free_page(GFP_KERNEL); if (!buf.dirent) - return -ENOMEM; + return nfserrno(-ENOMEM); offset = *offsetp; while (1) { + struct inode *dir_inode = file->f_path.dentry->d_inode; unsigned int reclen; cdp->err = nfserr_eof; /* will be cleared on successful read */ @@ -1924,26 +1925,38 @@ static int nfsd_buffered_readdir(struct file *file, filldir_t func, if (!size) break; + /* + * Various filldir functions may end up calling back into + * lookup_one_len() and the file system's ->lookup() method. + * These expect i_mutex to be held, as it would within readdir. + */ + host_err = mutex_lock_killable(&dir_inode->i_mutex); + if (host_err) + break; + de = (struct buffered_dirent *)buf.dirent; while (size > 0) { offset = de->offset; if (func(cdp, de->name, de->namlen, de->offset, de->ino, de->d_type)) - goto done; + break; if (cdp->err != nfs_ok) - goto done; + break; reclen = ALIGN(sizeof(*de) + de->namlen, sizeof(u64)); size -= reclen; de = (struct buffered_dirent *)((char *)de + reclen); } + mutex_unlock(&dir_inode->i_mutex); + if (size > 0) /* We bailed out early */ + break; + offset = vfs_llseek(file, 0, SEEK_CUR); } - done: free_page((unsigned long)(buf.dirent)); if (host_err) -- cgit v1.2.1