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SubjectRe: [PATCH 2/2] syslog: use defined constants instead of raw numbers
Quoting Kees Cook (kees.cook@canonical.com):
> Right now the syslog "type" actions are just raw numbers which makes
> the source difficult to follow. This patch replaces the raw numbers
> with defined constants for some level of sanity.
>
> Signed-off-by: Kees Cook <kees.cook@canonical.com>

yes please!

Acked-by: Serge Hallyn <serue@us.ibm.com>

> ---
> fs/proc/kmsg.c | 11 ++++++-----
> include/linux/syslog.h | 23 +++++++++++++++++++++++
> kernel/printk.c | 45 +++++++++++++++++++--------------------------
> security/commoncap.c | 5 +++--
> security/selinux/hooks.c | 21 +++++++++++----------
> 5 files changed, 62 insertions(+), 43 deletions(-)
>
> diff --git a/fs/proc/kmsg.c b/fs/proc/kmsg.c
> index 4a08999..1ac9d2b 100644
> --- a/fs/proc/kmsg.c
> +++ b/fs/proc/kmsg.c
> @@ -21,27 +21,28 @@ extern wait_queue_head_t log_wait;
>
> static int kmsg_open(struct inode * inode, struct file * file)
> {
> - return do_syslog(1, NULL, 0, 1);
> + return do_syslog(SYSLOG_ACTION_OPEN, NULL, 0, 1);
> }
>
> static int kmsg_release(struct inode * inode, struct file * file)
> {
> - (void) do_syslog(0, NULL, 0, 1);
> + (void) do_syslog(SYSLOG_ACTION_CLOSE, NULL, 0, 1);
> return 0;
> }
>
> static ssize_t kmsg_read(struct file *file, char __user *buf,
> size_t count, loff_t *ppos)
> {
> - if ((file->f_flags & O_NONBLOCK) && !do_syslog(9, NULL, 0, 1))
> + if ((file->f_flags & O_NONBLOCK) &&
> + !do_syslog(SYSLOG_ACTION_SIZE_UNREAD, NULL, 0, 1))
> return -EAGAIN;
> - return do_syslog(2, buf, count, 1);
> + return do_syslog(SYSLOG_ACTION_READ, buf, count, 1);
> }
>
> static unsigned int kmsg_poll(struct file *file, poll_table *wait)
> {
> poll_wait(file, &log_wait, wait);
> - if (do_syslog(9, NULL, 0, 1))
> + if (do_syslog(SYSLOG_ACTION_SIZE_UNREAD, NULL, 0, 1))
> return POLLIN | POLLRDNORM;
> return 0;
> }
> diff --git a/include/linux/syslog.h b/include/linux/syslog.h
> index f8c9d94..8c2c422 100644
> --- a/include/linux/syslog.h
> +++ b/include/linux/syslog.h
> @@ -21,6 +21,29 @@
> #ifndef _LINUX_SYSLOG_H
> #define _LINUX_SYSLOG_H
>
> +/* Close the log. Currently a NOP. */
> +#define SYSLOG_ACTION_CLOSE 0
> +/* Open the log. Currently a NOP. */
> +#define SYSLOG_ACTION_OPEN 1
> +/* Read from the log. */
> +#define SYSLOG_ACTION_READ 2
> +/* Read all messages remaining in the ring buffer. */
> +#define SYSLOG_ACTION_READ_ALL 3
> +/* Read and clear all messages remaining in the ring buffer */
> +#define SYSLOG_ACTION_READ_CLEAR 4
> +/* Clear ring buffer. */
> +#define SYSLOG_ACTION_CLEAR 5
> +/* Disable printk's to console */
> +#define SYSLOG_ACTION_CONSOLE_OFF 6
> +/* Enable printk's to console */
> +#define SYSLOG_ACTION_CONSOLE_ON 7
> +/* Set level of messages printed to console */
> +#define SYSLOG_ACTION_CONSOLE_LEVEL 8
> +/* Return number of unread characters in the log buffer */
> +#define SYSLOG_ACTION_SIZE_UNREAD 9
> +/* Return size of the log buffer */
> +#define SYSLOG_ACTION_SIZE_BUFFER 10
> +
> int do_syslog(int type, char __user *buf, int count, int from_file);
>
> #endif /* _LINUX_SYSLOG_H */
> diff --git a/kernel/printk.c b/kernel/printk.c
> index 4bc1412..ca1d970 100644
> --- a/kernel/printk.c
> +++ b/kernel/printk.c
> @@ -259,21 +259,6 @@ static inline void boot_delay_msec(void)
> }
> #endif
>
> -/*
> - * Commands to do_syslog:
> - *
> - * 0 -- Close the log. Currently a NOP.
> - * 1 -- Open the log. Currently a NOP.
> - * 2 -- Read from the log.
> - * 3 -- Read all messages remaining in the ring buffer.
> - * 4 -- Read and clear all messages remaining in the ring buffer
> - * 5 -- Clear ring buffer.
> - * 6 -- Disable printk's to console
> - * 7 -- Enable printk's to console
> - * 8 -- Set level of messages printed to console
> - * 9 -- Return number of unread characters in the log buffer
> - * 10 -- Return size of the log buffer
> - */
> int do_syslog(int type, char __user *buf, int len, int from_file)
> {
> unsigned i, j, limit, count;
> @@ -286,11 +271,11 @@ int do_syslog(int type, char __user *buf, int len, int from_file)
> return error;
>
> switch (type) {
> - case 0: /* Close log */
> + case SYSLOG_ACTION_CLOSE: /* Close log */
> break;
> - case 1: /* Open log */
> + case SYSLOG_ACTION_OPEN: /* Open log */
> break;
> - case 2: /* Read from log */
> + case SYSLOG_ACTION_READ: /* Read from log */
> error = -EINVAL;
> if (!buf || len < 0)
> goto out;
> @@ -321,10 +306,12 @@ int do_syslog(int type, char __user *buf, int len, int from_file)
> if (!error)
> error = i;
> break;
> - case 4: /* Read/clear last kernel messages */
> + /* Read/clear last kernel messages */
> + case SYSLOG_ACTION_READ_CLEAR:
> do_clear = 1;
> /* FALL THRU */
> - case 3: /* Read last kernel messages */
> + /* Read last kernel messages */
> + case SYSLOG_ACTION_READ_ALL:
> error = -EINVAL;
> if (!buf || len < 0)
> goto out;
> @@ -377,21 +364,25 @@ int do_syslog(int type, char __user *buf, int len, int from_file)
> }
> }
> break;
> - case 5: /* Clear ring buffer */
> + /* Clear ring buffer */
> + case SYSLOG_ACTION_CLEAR:
> logged_chars = 0;
> break;
> - case 6: /* Disable logging to console */
> + /* Disable logging to console */
> + case SYSLOG_ACTION_CONSOLE_OFF:
> if (saved_console_loglevel == -1)
> saved_console_loglevel = console_loglevel;
> console_loglevel = minimum_console_loglevel;
> break;
> - case 7: /* Enable logging to console */
> + /* Enable logging to console */
> + case SYSLOG_ACTION_CONSOLE_ON:
> if (saved_console_loglevel != -1) {
> console_loglevel = saved_console_loglevel;
> saved_console_loglevel = -1;
> }
> break;
> - case 8: /* Set level of messages printed to console */
> + /* Set level of messages printed to console */
> + case SYSLOG_ACTION_CONSOLE_LEVEL:
> error = -EINVAL;
> if (len < 1 || len > 8)
> goto out;
> @@ -402,10 +393,12 @@ int do_syslog(int type, char __user *buf, int len, int from_file)
> saved_console_loglevel = -1;
> error = 0;
> break;
> - case 9: /* Number of chars in the log buffer */
> + /* Number of chars in the log buffer */
> + case SYSLOG_ACTION_SIZE_UNREAD:
> error = log_end - log_start;
> break;
> - case 10: /* Size of the log buffer */
> + /* Size of the log buffer */
> + case SYSLOG_ACTION_SIZE_BUFFER:
> error = log_buf_len;
> break;
> default:
> diff --git a/security/commoncap.c b/security/commoncap.c
> index aaf123f..0705afe 100644
> --- a/security/commoncap.c
> +++ b/security/commoncap.c
> @@ -897,9 +897,10 @@ error:
> int cap_syslog(int type, int from_file)
> {
> /* /proc/kmsg can open be opened by CAP_SYS_ADMIN */
> - if (type != 1 && from_file)
> + if (type != SYSLOG_ACTION_OPEN && from_file)
> return 0;
> - if ((type != 3 && type != 10) && !capable(CAP_SYS_ADMIN))
> + if ((type != SYSLOG_ACTION_READ_ALL &&
> + type != SYSLOG_ACTION_SIZE_BUFFER) && !capable(CAP_SYS_ADMIN))
> return -EPERM;
> return 0;
> }
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 744785c..d242ab7 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -2059,20 +2059,21 @@ static int selinux_syslog(int type, int from_file)
> return rc;
>
> switch (type) {
> - case 3: /* Read last kernel messages */
> - case 10: /* Return size of the log buffer */
> + case SYSLOG_ACTION_READ_ALL: /* Read last kernel messages */
> + case SYSLOG_ACTION_SIZE_BUFFER: /* Return size of the log buffer */
> rc = task_has_system(current, SYSTEM__SYSLOG_READ);
> break;
> - case 6: /* Disable logging to console */
> - case 7: /* Enable logging to console */
> - case 8: /* Set level of messages printed to console */
> + case SYSLOG_ACTION_CONSOLE_OFF: /* Disable logging to console */
> + case SYSLOG_ACTION_CONSOLE_ON: /* Enable logging to console */
> + /* Set level of messages printed to console */
> + case SYSLOG_ACTION_CONSOLE_LEVEL:
> rc = task_has_system(current, SYSTEM__SYSLOG_CONSOLE);
> break;
> - case 0: /* Close log */
> - case 1: /* Open log */
> - case 2: /* Read from log */
> - case 4: /* Read/clear last kernel messages */
> - case 5: /* Clear ring buffer */
> + case SYSLOG_ACTION_CLOSE: /* Close log */
> + case SYSLOG_ACTION_OPEN: /* Open log */
> + case SYSLOG_ACTION_READ: /* Read from log */
> + case SYSLOG_ACTION_READ_CLEAR: /* Read/clear last kernel messages */
> + case SYSLOG_ACTION_CLEAR: /* Clear ring buffer */
> default:
> rc = task_has_system(current, SYSTEM__SYSLOG_MOD);
> break;
> --
> 1.6.5
>
>
> --
> Kees Cook
> Ubuntu Security Team


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