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    Subject[PATCH] fs: Preserve error code in get_empty_filp()
    Date
    From: Anatol Pomazau <anatol@google.com>

    Allocating a file structure in function get_empty_filp() might fail because
    of several reasons:
    - not enough memory for file structures
    - operation is not allowed
    - user is over its limit

    Currently the function returns NULL in all cases and we loose the exact
    reason of the error. All callers of get_empty_filp() assume that the function
    can fail with ENFILE only.

    Return error through pointer. Change all callers to preserve this error code.

    Signed-off-by: Anatol Pomozov <anatol.pomozov@gmail.com>
    Reviewed-by: "Theodore Ts'o" <tytso@mit.edu>
    ---
    arch/ia64/kernel/perfmon.c | 4 ++--
    fs/anon_inodes.c | 5 +++--
    fs/file_table.c | 23 +++++++++++++++--------
    fs/hugetlbfs/inode.c | 5 +++--
    fs/namei.c | 4 ++--
    fs/open.c | 5 ++---
    fs/pipe.c | 9 +++++----
    ipc/shm.c | 4 +++-
    mm/shmem.c | 5 +++--
    net/socket.c | 4 ++--
    10 files changed, 40 insertions(+), 28 deletions(-)

    diff --git a/arch/ia64/kernel/perfmon.c b/arch/ia64/kernel/perfmon.c
    index 3fa4bc5..da2dcce 100644
    --- a/arch/ia64/kernel/perfmon.c
    +++ b/arch/ia64/kernel/perfmon.c
    @@ -2221,9 +2221,9 @@ pfm_alloc_file(pfm_context_t *ctx)
    d_add(path.dentry, inode);

    file = alloc_file(&path, FMODE_READ, &pfm_file_ops);
    - if (!file) {
    + if (IS_ERR(file)) {
    path_put(&path);
    - return ERR_PTR(-ENFILE);
    + return file;
    }

    file->f_flags = O_RDONLY;
    diff --git a/fs/anon_inodes.c b/fs/anon_inodes.c
    index 28d39fb..73536e3 100644
    --- a/fs/anon_inodes.c
    +++ b/fs/anon_inodes.c
    @@ -160,10 +160,11 @@ struct file *anon_inode_getfile(const char *name,

    d_instantiate(path.dentry, anon_inode_inode);

    - error = -ENFILE;
    file = alloc_file(&path, OPEN_FMODE(flags), fops);
    - if (!file)
    + if (IS_ERR(file)) {
    + error = PTR_ERR(file);
    goto err_dput;
    + }
    file->f_mapping = anon_inode_inode->i_mapping;

    file->f_pos = 0;
    diff --git a/fs/file_table.c b/fs/file_table.c
    index b3fc4d6..5e65706 100644
    --- a/fs/file_table.c
    +++ b/fs/file_table.c
    @@ -94,8 +94,8 @@ int proc_nr_files(ctl_table *table, int write,
    #endif

    /* Find an unused file structure and return a pointer to it.
    - * Returns NULL, if there are no more free file structures or
    - * we run out of memory.
    + * Returns error pointer if some error happend e.g. we over file
    + * structures limit, run out of memory or operation is not permitted.
    *
    * Be very careful using this. You are responsible for
    * getting write access to any mount that you might assign
    @@ -108,6 +108,7 @@ struct file *get_empty_filp(void)
    const struct cred *cred = current_cred();
    static long old_max;
    struct file * f;
    + int error;

    /*
    * Privileged users can go above max_files
    @@ -117,18 +118,24 @@ struct file *get_empty_filp(void)
    * percpu_counters are inaccurate. Do an expensive check before
    * we go and fail.
    */
    - if (percpu_counter_sum_positive(&nr_files) >= files_stat.max_files)
    + if (percpu_counter_sum_positive(&nr_files) >= files_stat.max_files) {
    + error = -ENFILE;
    goto over;
    + }
    }

    f = kmem_cache_zalloc(filp_cachep, GFP_KERNEL);
    - if (f == NULL)
    + if (f == NULL) {
    + error = -ENOMEM;
    goto fail;
    + }

    percpu_counter_inc(&nr_files);
    f->f_cred = get_cred(cred);
    - if (security_file_alloc(f))
    + if (security_file_alloc(f)) {
    + error = -EPERM;
    goto fail_sec;
    + }

    INIT_LIST_HEAD(&f->f_u.fu_list);
    atomic_long_set(&f->f_count, 1);
    @@ -149,7 +156,7 @@ over:
    fail_sec:
    file_free(f);
    fail:
    - return NULL;
    + return ERR_PTR(error);
    }

    /**
    @@ -173,8 +180,8 @@ struct file *alloc_file(struct path *path, fmode_t mode,
    struct file *file;

    file = get_empty_filp();
    - if (!file)
    - return NULL;
    + if (IS_ERR(file))
    + return file;

    file->f_path = *path;
    file->f_mapping = path->dentry->d_inode->i_mapping;
    diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
    index 8349a89..5ec849b 100644
    --- a/fs/hugetlbfs/inode.c
    +++ b/fs/hugetlbfs/inode.c
    @@ -984,11 +984,12 @@ struct file *hugetlb_file_setup(const char *name, unsigned long addr,
    inode->i_size = size;
    clear_nlink(inode);

    - error = -ENFILE;
    file = alloc_file(&path, FMODE_WRITE | FMODE_READ,
    &hugetlbfs_file_operations);
    - if (!file)
    + if (IS_ERR(file)) {
    + error = PTR_ERR(file);
    goto out_dentry; /* inode is already attached */
    + }

    return file;

    diff --git a/fs/namei.c b/fs/namei.c
    index 2ccc35c..b77bdca 100644
    --- a/fs/namei.c
    +++ b/fs/namei.c
    @@ -2753,8 +2753,8 @@ static struct file *path_openat(int dfd, const char *pathname,
    int error;

    file = get_empty_filp();
    - if (!file)
    - return ERR_PTR(-ENFILE);
    + if (IS_ERR(file))
    + return file;

    file->f_flags = op->open_flag;

    diff --git a/fs/open.c b/fs/open.c
    index 1e914b3..195bdab 100644
    --- a/fs/open.c
    +++ b/fs/open.c
    @@ -777,10 +777,9 @@ struct file *dentry_open(const struct path *path, int flags,
    /* We must always pass in a valid mount pointer. */
    BUG_ON(!path->mnt);

    - error = -ENFILE;
    f = get_empty_filp();
    - if (f == NULL)
    - return ERR_PTR(error);
    + if (IS_ERR(f))
    + return f;

    f->f_flags = flags;
    f->f_path = *path;
    diff --git a/fs/pipe.c b/fs/pipe.c
    index 95cbd6b..429f2db 100644
    --- a/fs/pipe.c
    +++ b/fs/pipe.c
    @@ -1037,10 +1037,11 @@ struct file *create_write_pipe(int flags)

    d_instantiate(path.dentry, inode);

    - err = -ENFILE;
    f = alloc_file(&path, FMODE_WRITE, &write_pipefifo_fops);
    - if (!f)
    + if (IS_ERR(f)) {
    + err = PTR_ERR(f);
    goto err_dentry;
    + }
    f->f_mapping = inode->i_mapping;

    f->f_flags = O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT));
    @@ -1072,8 +1073,8 @@ struct file *create_read_pipe(struct file *wrf, int flags)
    /* Grab pipe from the writer */
    struct file *f = alloc_file(&wrf->f_path, FMODE_READ,
    &read_pipefifo_fops);
    - if (!f)
    - return ERR_PTR(-ENFILE);
    + if (IS_ERR(f))
    + return f;

    path_get(&wrf->f_path);
    f->f_flags = O_RDONLY | (flags & O_NONBLOCK);
    diff --git a/ipc/shm.c b/ipc/shm.c
    index 00faa05..c8eee21 100644
    --- a/ipc/shm.c
    +++ b/ipc/shm.c
    @@ -1039,8 +1039,10 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr,
    is_file_hugepages(shp->shm_file) ?
    &shm_file_operations_huge :
    &shm_file_operations);
    - if (!file)
    + if (IS_ERR(file)) {
    + err = PTR_ERR(file);
    goto out_free;
    + }

    file->private_data = sfd;
    file->f_mapping = shp->shm_file->f_mapping;
    diff --git a/mm/shmem.c b/mm/shmem.c
    index d4e184e..cd814ee 100644
    --- a/mm/shmem.c
    +++ b/mm/shmem.c
    @@ -2948,11 +2948,12 @@ struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags
    goto put_dentry;
    #endif

    - error = -ENFILE;
    file = alloc_file(&path, FMODE_WRITE | FMODE_READ,
    &shmem_file_operations);
    - if (!file)
    + if (IS_ERR(file)) {
    + error = PTR_ERR(file);
    goto put_dentry;
    + }

    return file;

    diff --git a/net/socket.c b/net/socket.c
    index dfe5b66..e80eb83 100644
    --- a/net/socket.c
    +++ b/net/socket.c
    @@ -369,12 +369,12 @@ static int sock_alloc_file(struct socket *sock, struct file **f, int flags)

    file = alloc_file(&path, FMODE_READ | FMODE_WRITE,
    &socket_file_ops);
    - if (unlikely(!file)) {
    + if (unlikely(IS_ERR(file))) {
    /* drop dentry, keep inode */
    ihold(path.dentry->d_inode);
    path_put(&path);
    put_unused_fd(fd);
    - return -ENFILE;
    + return PTR_ERR(file);
    }

    sock->file = file;
    --
    1.7.11.3


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