From 7c7dce9209161eb260cdf9e9172f72c3a02379e6 Mon Sep 17 00:00:00 2001 From: Alexander Viro Date: Sat, 14 Jan 2006 15:29:55 -0500 Subject: [PATCH] [PATCH] Fix double decrement of mqueue_mnt->mnt_count in sys_mq_open Fixed the refcounting on failure exits in sys_mq_open() and cleaned the logics up. Rules are actually pretty simple - dentry_open() expects vfsmount and dentry to be pinned down and it either transfers them into created struct file or drops them. Old code had been very confused in that area - if dentry_open() had failed either in do_open() or do_create(), we ended up dentry and mqueue_mnt dropped twice, once by dentry_open() cleanup and then by sys_mq_open(). Fix consists of making the rules for do_create() and do_open() same as for dentry_open() and updating the sys_mq_open() accordingly; that actually leads to more straightforward code and less work on normal path. Signed-off-by: Al Viro Signed-off-by: Linus Torvalds --- ipc/mqueue.c | 59 +++++++++++++++++++++++++++++----------------------- 1 file changed, 33 insertions(+), 26 deletions(-) diff --git a/ipc/mqueue.c b/ipc/mqueue.c index 4e776f9c80e..59302fc3643 100644 --- a/ipc/mqueue.c +++ b/ipc/mqueue.c @@ -599,15 +599,16 @@ static int mq_attr_ok(struct mq_attr *attr) static struct file *do_create(struct dentry *dir, struct dentry *dentry, int oflag, mode_t mode, struct mq_attr __user *u_attr) { - struct file *filp; struct mq_attr attr; int ret; - if (u_attr != NULL) { + if (u_attr) { + ret = -EFAULT; if (copy_from_user(&attr, u_attr, sizeof(attr))) - return ERR_PTR(-EFAULT); + goto out; + ret = -EINVAL; if (!mq_attr_ok(&attr)) - return ERR_PTR(-EINVAL); + goto out; /* store for use during create */ dentry->d_fsdata = &attr; } @@ -616,13 +617,14 @@ static struct file *do_create(struct dentry *dir, struct dentry *dentry, ret = vfs_create(dir->d_inode, dentry, mode, NULL); dentry->d_fsdata = NULL; if (ret) - return ERR_PTR(ret); + goto out; - filp = dentry_open(dentry, mqueue_mnt, oflag); - if (!IS_ERR(filp)) - dget(dentry); + return dentry_open(dentry, mqueue_mnt, oflag); - return filp; +out: + dput(dentry); + mntput(mqueue_mnt); + return ERR_PTR(ret); } /* Opens existing queue */ @@ -630,20 +632,20 @@ static struct file *do_open(struct dentry *dentry, int oflag) { static int oflag2acc[O_ACCMODE] = { MAY_READ, MAY_WRITE, MAY_READ | MAY_WRITE }; - struct file *filp; - if ((oflag & O_ACCMODE) == (O_RDWR | O_WRONLY)) + if ((oflag & O_ACCMODE) == (O_RDWR | O_WRONLY)) { + dput(dentry); + mntput(mqueue_mnt); return ERR_PTR(-EINVAL); + } - if (permission(dentry->d_inode, oflag2acc[oflag & O_ACCMODE], NULL)) + if (permission(dentry->d_inode, oflag2acc[oflag & O_ACCMODE], NULL)) { + dput(dentry); + mntput(mqueue_mnt); return ERR_PTR(-EACCES); + } - filp = dentry_open(dentry, mqueue_mnt, oflag); - - if (!IS_ERR(filp)) - dget(dentry); - - return filp; + return dentry_open(dentry, mqueue_mnt, oflag); } asmlinkage long sys_mq_open(const char __user *u_name, int oflag, mode_t mode, @@ -671,17 +673,20 @@ asmlinkage long sys_mq_open(const char __user *u_name, int oflag, mode_t mode, if (oflag & O_CREAT) { if (dentry->d_inode) { /* entry already exists */ - filp = (oflag & O_EXCL) ? ERR_PTR(-EEXIST) : - do_open(dentry, oflag); + error = -EEXIST; + if (oflag & O_EXCL) + goto out; + filp = do_open(dentry, oflag); } else { filp = do_create(mqueue_mnt->mnt_root, dentry, oflag, mode, u_attr); } - } else - filp = (dentry->d_inode) ? do_open(dentry, oflag) : - ERR_PTR(-ENOENT); - - dput(dentry); + } else { + error = -ENOENT; + if (!dentry->d_inode) + goto out; + filp = do_open(dentry, oflag); + } if (IS_ERR(filp)) { error = PTR_ERR(filp); @@ -692,8 +697,10 @@ asmlinkage long sys_mq_open(const char __user *u_name, int oflag, mode_t mode, fd_install(fd, filp); goto out_upsem; -out_putfd: +out: + dput(dentry); mntput(mqueue_mnt); +out_putfd: put_unused_fd(fd); out_err: fd = error; -- 2.20.1