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tty: audit: Ignore current association for audit push

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In canonical read mode, each line read and logged is pushed separately
with tty_audit_push(). For all single-threaded processes and multi-threaded
processes reading from only one tty, this patch has no effect; the last line
read will still be the entry pushed to the audit log because the tty
association cannot have changed between tty_audit_add_data() and
tty_audit_push().

For multi-threaded processes reading from different ttys concurrently,
the audit log will have mixed log entries anyway. Consider two ttys
audited concurrently:

CPU0                           CPU1
----------                     ------------
tty_audit_add_data(ttyA)
                               tty_audit_add_data(ttyB)
tty_audit_push()
                               tty_audit_add_data(ttyB)
                               tty_audit_push()

This patch will now cause the ttyB output to be split into separate
audit log entries.

However, this possibility is equally likely without this patch:

CPU0                           CPU1
----------                     ------------
                               tty_audit_add_data(ttyB)
tty_audit_add_data(ttyA)
tty_audit_push()
                               tty_audit_add_data(ttyB)
                               tty_audit_push()

Mixed canonical and non-canonical reads have similar races.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Peter Hurley 2016-01-09 22:55:30 -08:00 committed by Greg Kroah-Hartman
parent f229c2c161
commit b50819f437
3 changed files with 6 additions and 11 deletions
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2
drivers/tty/n_tty.c
View file

@ -2072,7 +2072,7 @@ static int canon_copy_from_read_buf(struct tty_struct *tty,
ldata->line_start = ldata->read_tail;
else
ldata->push = 0;
tty_audit_push(tty);
tty_audit_push();
}
return 0;
}

11
drivers/tty/tty_audit.c
View file

@ -313,9 +313,9 @@ void tty_audit_add_data(struct tty_struct *tty, const void *data, size_t size)
/**
* tty_audit_push - Push buffered data out
*
* Make sure no audit data is pending for @tty on the current process.
* Make sure no audit data is pending on the current process.
*/
void tty_audit_push(struct tty_struct *tty)
void tty_audit_push(void)
{
struct tty_audit_buf *buf;
unsigned long flags;
@ -331,13 +331,8 @@ void tty_audit_push(struct tty_struct *tty)
spin_unlock_irqrestore(&current->sighand->siglock, flags);
if (buf) {
int major, minor;
major = tty->driver->major;
minor = tty->driver->minor_start + tty->index;
mutex_lock(&buf->mutex);
if (buf->major == major && buf->minor == minor)
tty_audit_buf_push(buf);
tty_audit_buf_push(buf);
mutex_unlock(&buf->mutex);
tty_audit_buf_put(buf);
}

4
include/linux/tty.h
View file

@ -597,7 +597,7 @@ extern void tty_audit_add_data(struct tty_struct *tty, const void *data,
extern void tty_audit_exit(void);
extern void tty_audit_fork(struct signal_struct *sig);
extern void tty_audit_tiocsti(struct tty_struct *tty, char ch);
extern void tty_audit_push(struct tty_struct *tty);
extern void tty_audit_push(void);
extern int tty_audit_push_current(void);
#else
static inline void tty_audit_add_data(struct tty_struct *tty, const void *data,
@ -613,7 +613,7 @@ static inline void tty_audit_exit(void)
static inline void tty_audit_fork(struct signal_struct *sig)
{
}
static inline void tty_audit_push(struct tty_struct *tty)
static inline void tty_audit_push(void)
{
}
static inline int tty_audit_push_current(void)