[PATCH] fix file and descriptor handling in perfmon

Races galore...  General rule: as soon as it's in descriptor table,
it's over; another thread might have started IO on it/dup2() it
elsewhere/dup2() something *over* it/etc.  fd_install() is the very
last step one should take - it's a point of no return.

Besides, the damn thing leaked on failure exits...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/arch/ia64/kernel/perfmon.c b/arch/ia64/kernel/perfmon.c
index 7fbb51e10bbe04e70c2cc66570400f3569f3804c..c1ad27de2dd2080e0bdea8a845147fcc6f855dba 100644 (file)
--- a/arch/ia64/kernel/perfmon.c
+++ b/arch/ia64/kernel/perfmon.c
@@ -867,7 +867,7 @@ pfm_rvfree(void *mem, unsigned long size)
 }
 
 static pfm_context_t *
-pfm_context_alloc(void)
+pfm_context_alloc(int ctx_flags)
 {
        pfm_context_t *ctx;
 
@@ -878,6 +878,46 @@ pfm_context_alloc(void)
        ctx = kzalloc(sizeof(pfm_context_t), GFP_KERNEL);
        if (ctx) {
                DPRINT(("alloc ctx @%p\n", ctx));
+
+               /*
+                * init context protection lock
+                */
+               spin_lock_init(&ctx->ctx_lock);
+
+               /*
+                * context is unloaded
+                */
+               ctx->ctx_state = PFM_CTX_UNLOADED;
+
+               /*
+                * initialization of context's flags
+                */
+               ctx->ctx_fl_block       = (ctx_flags & PFM_FL_NOTIFY_BLOCK) ? 1 : 0;
+               ctx->ctx_fl_system      = (ctx_flags & PFM_FL_SYSTEM_WIDE) ? 1: 0;
+               ctx->ctx_fl_no_msg      = (ctx_flags & PFM_FL_OVFL_NO_MSG) ? 1: 0;
+               /*
+                * will move to set properties
+                * ctx->ctx_fl_excl_idle   = (ctx_flags & PFM_FL_EXCL_IDLE) ? 1: 0;
+                */
+
+               /*
+                * init restart semaphore to locked
+                */
+               init_completion(&ctx->ctx_restart_done);
+
+               /*
+                * activation is used in SMP only
+                */
+               ctx->ctx_last_activation = PFM_INVALID_ACTIVATION;
+               SET_LAST_CPU(ctx, -1);
+
+               /*
+                * initialize notification message queue
+                */
+               ctx->ctx_msgq_head = ctx->ctx_msgq_tail = 0;
+               init_waitqueue_head(&ctx->ctx_msgq_wait);
+               init_waitqueue_head(&ctx->ctx_zombieq);
+
        }
        return ctx;
 }
@@ -2165,28 +2205,21 @@ static struct dentry_operations pfmfs_dentry_operations = {
 };
 
 
-static int
-pfm_alloc_fd(struct file **cfile)
+static struct file *
+pfm_alloc_file(pfm_context_t *ctx)
 {
-       int fd, ret = 0;
-       struct file *file = NULL;
-       struct inode * inode;
+       struct file *file;
+       struct inode *inode;
+       struct dentry *dentry;
        char name[32];
        struct qstr this;
 
-       fd = get_unused_fd();
-       if (fd < 0) return -ENFILE;
-
-       ret = -ENFILE;
-
-       file = get_empty_filp();
-       if (!file) goto out;
-
        /*
         * allocate a new inode
         */
        inode = new_inode(pfmfs_mnt->mnt_sb);
-       if (!inode) goto out;
+       if (!inode)
+               return ERR_PTR(-ENOMEM);
 
        DPRINT(("new inode ino=%ld @%p\n", inode->i_ino, inode));
 
@@ -2199,59 +2232,28 @@ pfm_alloc_fd(struct file **cfile)
        this.len  = strlen(name);
        this.hash = inode->i_ino;
 
-       ret = -ENOMEM;
-
        /*
         * allocate a new dcache entry
         */
-       file->f_path.dentry = d_alloc(pfmfs_mnt->mnt_sb->s_root, &this);
-       if (!file->f_path.dentry) goto out;
+       dentry = d_alloc(pfmfs_mnt->mnt_sb->s_root, &this);
+       if (!dentry) {
+               iput(inode);
+               return ERR_PTR(-ENOMEM);
+       }
 
-       file->f_path.dentry->d_op = &pfmfs_dentry_operations;
+       dentry->d_op = &pfmfs_dentry_operations;
+       d_add(dentry, inode);
 
-       d_add(file->f_path.dentry, inode);
-       file->f_path.mnt = mntget(pfmfs_mnt);
-       file->f_mapping = inode->i_mapping;
+       file = alloc_file(pfmfs_mnt, dentry, FMODE_READ, &pfm_file_ops);
+       if (!file) {
+               dput(dentry);
+               return ERR_PTR(-ENFILE);
+       }
 
-       file->f_op    = &pfm_file_ops;
-       file->f_mode  = FMODE_READ;
        file->f_flags = O_RDONLY;
-       file->f_pos   = 0;
-
-       /*
-        * may have to delay until context is attached?
-        */
-       fd_install(fd, file);
-
-       /*
-        * the file structure we will use
-        */
-       *cfile = file;
-
-       return fd;
-out:
-       if (file) put_filp(file);
-       put_unused_fd(fd);
-       return ret;
-}
-
-static void
-pfm_free_fd(int fd, struct file *file)
-{
-       struct files_struct *files = current->files;
-       struct fdtable *fdt;
+       file->private_data = ctx;
 
-       /* 
-        * there ie no fd_uninstall(), so we do it here
-        */
-       spin_lock(&files->file_lock);
-       fdt = files_fdtable(files);
-       rcu_assign_pointer(fdt->fd[fd], NULL);
-       spin_unlock(&files->file_lock);
-
-       if (file)
-               put_filp(file);
-       put_unused_fd(fd);
+       return file;
 }
 
 static int
@@ -2475,6 +2477,7 @@ pfm_setup_buffer_fmt(struct task_struct *task, struct file *filp, pfm_context_t
 
        /* link buffer format and context */
        ctx->ctx_buf_fmt = fmt;
+       ctx->ctx_fl_is_sampling = 1; /* assume record() is defined */
 
        /*
         * check if buffer format wants to use perfmon buffer allocation/mapping service
@@ -2669,78 +2672,45 @@ pfm_context_create(pfm_context_t *ctx, void *arg, int count, struct pt_regs *reg
 {
        pfarg_context_t *req = (pfarg_context_t *)arg;
        struct file *filp;
+       struct path path;
        int ctx_flags;
+       int fd;
        int ret;
 
        /* let's check the arguments first */
        ret = pfarg_is_sane(current, req);
-       if (ret < 0) return ret;
+       if (ret < 0)
+               return ret;
 
        ctx_flags = req->ctx_flags;
 
        ret = -ENOMEM;
 
-       ctx = pfm_context_alloc();
-       if (!ctx) goto error;
+       fd = get_unused_fd();
+       if (fd < 0)
+               return fd;
 
-       ret = pfm_alloc_fd(&filp);
-       if (ret < 0) goto error_file;
+       ctx = pfm_context_alloc(ctx_flags);
+       if (!ctx)
+               goto error;
 
-       req->ctx_fd = ctx->ctx_fd = ret;
+       filp = pfm_alloc_file(ctx);
+       if (IS_ERR(filp)) {
+               ret = PTR_ERR(filp);
+               goto error_file;
+       }
 
-       /*
-        * attach context to file
-        */
-       filp->private_data = ctx;
+       req->ctx_fd = ctx->ctx_fd = fd;
 
        /*
         * does the user want to sample?
         */
        if (pfm_uuid_cmp(req->ctx_smpl_buf_id, pfm_null_uuid)) {
                ret = pfm_setup_buffer_fmt(current, filp, ctx, ctx_flags, 0, req);
-               if (ret) goto buffer_error;
+               if (ret)
+                       goto buffer_error;
        }
 
-       /*
-        * init context protection lock
-        */
-       spin_lock_init(&ctx->ctx_lock);
-
-       /*
-        * context is unloaded
-        */
-       ctx->ctx_state = PFM_CTX_UNLOADED;
-
-       /*
-        * initialization of context's flags
-        */
-       ctx->ctx_fl_block       = (ctx_flags & PFM_FL_NOTIFY_BLOCK) ? 1 : 0;
-       ctx->ctx_fl_system      = (ctx_flags & PFM_FL_SYSTEM_WIDE) ? 1: 0;
-       ctx->ctx_fl_is_sampling = ctx->ctx_buf_fmt ? 1 : 0; /* assume record() is defined */
-       ctx->ctx_fl_no_msg      = (ctx_flags & PFM_FL_OVFL_NO_MSG) ? 1: 0;
-       /*
-        * will move to set properties
-        * ctx->ctx_fl_excl_idle   = (ctx_flags & PFM_FL_EXCL_IDLE) ? 1: 0;
-        */
-
-       /*
-        * init restart semaphore to locked
-        */
-       init_completion(&ctx->ctx_restart_done);
-
-       /*
-        * activation is used in SMP only
-        */
-       ctx->ctx_last_activation = PFM_INVALID_ACTIVATION;
-       SET_LAST_CPU(ctx, -1);
-
-       /*
-        * initialize notification message queue
-        */
-       ctx->ctx_msgq_head = ctx->ctx_msgq_tail = 0;
-       init_waitqueue_head(&ctx->ctx_msgq_wait);
-       init_waitqueue_head(&ctx->ctx_zombieq);
-
        DPRINT(("ctx=%p flags=0x%x system=%d notify_block=%d excl_idle=%d no_msg=%d ctx_fd=%d \n",
                ctx,
                ctx_flags,
@@ -2755,10 +2725,14 @@ pfm_context_create(pfm_context_t *ctx, void *arg, int count, struct pt_regs *reg
         */
        pfm_reset_pmu_state(ctx);
 
+       fd_install(fd, filp);
+
        return 0;
 
 buffer_error:
-       pfm_free_fd(ctx->ctx_fd, filp);
+       path = filp->f_path;
+       put_filp(filp);
+       path_put(&path);
 
        if (ctx->ctx_buf_fmt) {
                pfm_buf_fmt_exit(ctx->ctx_buf_fmt, current, NULL, regs);
@@ -2767,6 +2741,7 @@ error_file:
        pfm_context_free(ctx);
 
 error:
+       put_unused_fd(fd);
        return ret;
 }