unimore/kernel-hacking-2024-linux-steffo
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AUDIT: Fix livelock in audit_serial().

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The tricks with atomic_t were bizarre. Just do it sensibly instead.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
This commit is contained in:
David Woodhouse 2005-07-15 12:56:03 +01:00
parent 351bb72259
commit d5b454f2c4
1 changed files with 10 additions and 11 deletions
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21
kernel/audit.c
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@ -610,26 +610,25 @@ static struct audit_buffer * audit_buffer_alloc(struct audit_context *ctx,
* (timestamp,serial) tuple is unique for each syscall and is live from
* syscall entry to syscall exit.
*
* Atomic values are only guaranteed to be 24-bit, so we count down.
*
* NOTE: Another possibility is to store the formatted records off the
* audit context (for those records that have a context), and emit them
* all at syscall exit. However, this could delay the reporting of
* significant errors until syscall exit (or never, if the system
* halts). */
unsigned int audit_serial(void)
{
static atomic_t serial = ATOMIC_INIT(0xffffff);
unsigned int a, b;
static spinlock_t serial_lock = SPIN_LOCK_UNLOCKED;
static unsigned int serial = 0;
do {
a = atomic_read(&serial);
if (atomic_dec_and_test(&serial))
atomic_set(&serial, 0xffffff);
b = atomic_read(&serial);
} while (b != a - 1);
unsigned long flags;
unsigned int ret;
return 0xffffff - b;
spin_lock_irqsave(&serial_lock, flags);
ret = serial++;
spin_unlock_irqrestore(&serial_lock, flags);
return ret;
}
static inline void audit_get_stamp(struct audit_context *ctx,