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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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4
include/linux/tty.h
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@@ -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)