PATCH [06/06] This patch introduces the .write seq operation for /proc/pid/semundo.
In order to simplify the locking strategy, the write operation is only allowed to 'current'. Signed-off-by: Nadia Derbey <[EMAIL PROTECTED]> --- fs/proc/base.c | 2 ipc/sem.c | 250 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++- 2 files changed, 250 insertions(+), 2 deletions(-) Index: linux-2.6.26-rc5-mm3/fs/proc/base.c =================================================================== --- linux-2.6.26-rc5-mm3.orig/fs/proc/base.c 2008-06-24 10:03:33.000000000 +0200 +++ linux-2.6.26-rc5-mm3/fs/proc/base.c 2008-06-24 13:21:44.000000000 +0200 @@ -2526,7 +2526,7 @@ static const struct pid_entry tgid_base_ INF("io", S_IRUGO, tgid_io_accounting), #endif #ifdef CONFIG_SYSVIPC - REG("semundo", S_IRUGO, semundo), + REG("semundo", S_IWUSR|S_IRUGO, semundo), #endif }; Index: linux-2.6.26-rc5-mm3/ipc/sem.c =================================================================== --- linux-2.6.26-rc5-mm3.orig/ipc/sem.c 2008-06-24 12:59:15.000000000 +0200 +++ linux-2.6.26-rc5-mm3/ipc/sem.c 2008-06-25 08:56:07.000000000 +0200 @@ -1554,7 +1554,27 @@ static int semundo_open(struct inode *in goto out_err; } - ulp = get_proc_ulp(task); + if (file->f_flags & O_WRONLY || file->f_flags & O_RDWR) { + /* + * Writing is only allowed to current + */ + if (task != current) { + put_task_struct(task); + ret = -EPERM; + goto out_err; + } + /* + * No need to increment the undo_list's refcnt: only current + * can be freeing it through exit, and we are current. + * Only signal through the ulp NULL pointer that it won't be + * necessary to decrement the refcnt during release. + * Actually, in this path the undo_list will be gotten during + * the write operation. + */ + ulp = NULL; + } else + ulp = get_proc_ulp(task); + ns = get_ipc_ns(task->nsproxy->ipc_ns); put_task_struct(task); @@ -1574,6 +1594,233 @@ out_err: return ret; } +/* Skip all spaces at the beginning of the buffer */ +static inline int skip_space(const char __user **buf, size_t *len) +{ + char c = 0; + while (*len) { + if (get_user(c, *buf)) + return -EFAULT; + if (c != '\t' && c != ' ') + break; + --*len; + ++*buf; + } + return c; +} + +/* Retrieve the first numerical value contained in the string. + * Note: The value is supposed to be a 32-bit integer. + */ +static inline int get_next_value(const char __user **buf, size_t *len, int *val) +{ +#define BUFLEN 11 + int err, neg = 0, left; + char s[BUFLEN], *p; + + err = skip_space(buf, len); + if (err < 0) + return err; + if (!*len) + return INT_MAX; + if (err == '\n') { + ++*buf; + --*len; + return INT_MAX; + } + if (err == '-') { + ++*buf; + --*len; + neg = 1; + } + + left = *len; + if (left > sizeof(s) - 1) + left = sizeof(s) - 1; + if (copy_from_user(s, *buf, left)) + return -EFAULT; + + s[left] = 0; + p = s; + if (*p < '0' || *p > '9') + return -EINVAL; + + *val = simple_strtoul(p, &p, 0); + if (neg) + *val = -(*val); + + left = p-s; + (*len) -= left; + (*buf) += left; + + return 0; +#undef BUFLEN +} + +/* + * Reads a line from /proc/self/semundo. + * Returns the number of undo values read (or errcode upon failure). + * @id: pointer to the semid (filled in with 1st field in the line) + * @array: semundo values (filled in iwth remaining fields in the line). + * @array_len: max # of expected semundo values + */ +static inline int semundo_readline(const char __user **buf, size_t *left, + int *id, short *array, int array_len) +{ + int i, val, err; + + /* Read semid */ + err = get_next_value(buf, left, id); + if (err) + return err; + + /* Read all (semundo-) values of a full line */ + for (i = 0; ; i++) { + err = get_next_value(buf, left, &val); + if (err < 0) + return err; + /* reached end of line or end of buffer */ + if (err == INT_MAX) + break; + /* Return an error if we get more values than expected */ + if (i < array_len) + array[i] = val; + else + return -EINVAL; + } + return i; +} + +/* + * sets or updates the undo values for the undo_list of a given semaphore id. + * This is exactly the same code sequence as sys_semtimedop if we have undos. + */ +static inline int semundo_update(struct ipc_namespace *ns, int semid, + short *array, int size) +{ + struct sem_undo *un; + struct sem_array *sma; + int ret = 0; + + un = find_alloc_undo(ns, semid); + if (IS_ERR(un)) { + ret = PTR_ERR(un); + goto out; + } + + /* lookup the sem_array */ + sma = sem_lock(ns, semid); + if (IS_ERR(sma)) { + ret = PTR_ERR(sma); + rcu_read_unlock(); + goto out; + } + + /* + * find_alloc_undo opened an rcu read section to protect un. + * Releasing it here is safe: + * . sem_lock is held, so we are protected against IPC_RMID + * . the refcnt won't fall to 0 since exit_sem only operates on + * current and we are the current. + */ + rcu_read_unlock(); + + /* + * semid identifiers are not unique - find_alloc_undo() may have + * allocated an undo structure, it was invalidated by an RMID and now + * a new array received the same id. + * Check and fail. + * This case can be detected checking un->semid. The existance of + * "un" itself is guaranteed by rcu. + */ + if (un->semid == -1) { + ret = -EIDRM; + goto out_unlock; + } + + /* + * If the number of values given does not match the number of + * semaphores in the array, consider this as an error. + */ + if (size != sma->sem_nsems) { + ret = -EINVAL; + goto out_unlock; + } + + /* update the undo values */ + while (--size >= 0) + un->semadj[size] = array[size]; + + /* maybe some queued-up processes were waiting for this */ + update_queue(sma); + +out_unlock: + sem_unlock(sma); +out: + return ret; +} + +/* + * write operation for /proc/self/semundo file + * + * Only current is allowed to write to its semundo file. + * + * The expected string format is: + * "<semID> <val1> <val2> ... <valN>" + * + * It sets (or updates) the sem_undo list for 'current' and the target + * <semID>, to the given 'undo' values. + * + * <semID> must match an existing semaphore array. + * The number of values following <semID> must match the number of semaphores + * in the corresponding array. + * + * Multiple semID's can be passed simultaneously: newline ('\n') is considered + * as a separator in that case. + * + * Note: it is not allowed to set the sem_undo list for a given semID using + * mutliple write calls. + */ +static ssize_t semundo_write(struct file *file, const char __user *buf, + size_t count, loff_t *ppos) +{ + struct seq_file *m = file->private_data; + short *array; + int err, max_sem, semid = 0; + size_t left = count; + struct undo_list_data *data = m->private; + struct ipc_namespace *ns = data->ipc_ns; + + if (data->undo_list) + /* Should never happen */ + return -EINVAL; + + max_sem = ns->sc_semmsl; + + array = kmalloc(sizeof(short)*max_sem, GFP_KERNEL); + if (array == NULL) + return -ENOMEM; + + while (left) { + int nval; + + nval = semundo_readline(&buf, &left, &semid, array, max_sem); + if (nval < 0) { + err = nval; + goto out; + } + + err = semundo_update(ns, semid, array, nval); + if (err) + goto out; + } + err = count - left; + +out: + kfree(array); + return err; +} + static int semundo_release(struct inode *inode, struct file *file) { struct seq_file *m = file->private_data; @@ -1590,6 +1837,7 @@ static int semundo_release(struct inode const struct file_operations proc_semundo_operations = { .open = semundo_open, .read = seq_read, + .write = semundo_write, .llseek = seq_lseek, .release = semundo_release, }; -- _______________________________________________ Containers mailing list [EMAIL PROTECTED] https://lists.linux-foundation.org/mailman/listinfo/containers _______________________________________________ Devel mailing list Devel@openvz.org https://openvz.org/mailman/listinfo/devel