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bpf: check that BPF programs run with preemption disabled 

Introduce cant_sleep() macro for annotation of functions that
cannot sleep.

Use it in BPF_PROG_RUN to catch execution of BPF programs in
preemptable context.

Suggested-by: Jann Horn <jannh@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Peter Zijlstra 2019-01-28 17:21:52 -08:00 committed by Daniel Borkmann
parent a5d9265e01
commit 568f196756
3 changed files with 41 additions and 3 deletions
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2
include/linux/filter.h
View File

@ -533,7 +533,7 @@ struct sk_filter {
struct bpf_prog *prog;
};
#define BPF_PROG_RUN(filter, ctx) (*(filter)->bpf_func)(ctx, (filter)->insnsi)
#define BPF_PROG_RUN(filter, ctx) ({ cant_sleep(); (*(filter)->bpf_func)(ctx, (filter)->insnsi); })
#define BPF_SKB_CB_LEN QDISC_CB_PRIV_LEN

14
include/linux/kernel.h
View File

@ -245,8 +245,10 @@ extern int _cond_resched(void);
#endif
#ifdef CONFIG_DEBUG_ATOMIC_SLEEP
void ___might_sleep(const char *file, int line, int preempt_offset);
void __might_sleep(const char *file, int line, int preempt_offset);
extern void ___might_sleep(const char *file, int line, int preempt_offset);
extern void __might_sleep(const char *file, int line, int preempt_offset);
extern void __cant_sleep(const char *file, int line, int preempt_offset);
/**
* might_sleep - annotation for functions that can sleep
*
@ -259,6 +261,13 @@ extern int _cond_resched(void);
*/
# define might_sleep() \
do { __might_sleep(__FILE__, __LINE__, 0); might_resched(); } while (0)
/**
* cant_sleep - annotation for functions that cannot sleep
*
* this macro will print a stack trace if it is executed with preemption enabled
*/
# define cant_sleep() \
do { __cant_sleep(__FILE__, __LINE__, 0); } while (0)
# define sched_annotate_sleep() (current->task_state_change = 0)
#else
static inline void ___might_sleep(const char *file, int line,
@ -266,6 +275,7 @@ extern int _cond_resched(void);
static inline void __might_sleep(const char *file, int line,
int preempt_offset) { }
# define might_sleep() do { might_resched(); } while (0)
# define cant_sleep() do { } while (0)
# define sched_annotate_sleep() do { } while (0)
#endif

28
kernel/sched/core.c
View File

@ -6162,6 +6162,34 @@ void ___might_sleep(const char *file, int line, int preempt_offset)
add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
}
EXPORT_SYMBOL(___might_sleep);
void __cant_sleep(const char *file, int line, int preempt_offset)
{
static unsigned long prev_jiffy;
if (irqs_disabled())
return;
if (!IS_ENABLED(CONFIG_PREEMPT_COUNT))
return;
if (preempt_count() > preempt_offset)
return;
if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
return;
prev_jiffy = jiffies;
printk(KERN_ERR "BUG: assuming atomic context at %s:%d\n", file, line);
printk(KERN_ERR "in_atomic(): %d, irqs_disabled(): %d, pid: %d, name: %s\n",
in_atomic(), irqs_disabled(),
current->pid, current->comm);
debug_show_held_locks(current);
dump_stack();
add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
}
EXPORT_SYMBOL_GPL(__cant_sleep);
#endif
#ifdef CONFIG_MAGIC_SYSRQ