on x86 system with net.core.bpf_jit_enable = 1
sudo tcpdump -i eth1 'tcp port 22'
causes the warning:
[ 56.766097] Possible unsafe locking scenario:
[ 56.766097]
[ 56.780146] CPU0
[ 56.786807] ----
[ 56.793188] lock(&(&vb->lock)->rlock);
[ 56.799593] <Interrupt>
[ 56.805889] lock(&(&vb->lock)->rlock);
[ 56.812266]
[ 56.812266] *** DEADLOCK ***
[ 56.812266]
[ 56.830670] 1 lock held by ksoftirqd/1/13:
[ 56.836838] #0: (rcu_read_lock){.+.+..}, at: [<ffffffff8118f44c>]
vm_unmap_aliases+0x8c/0x380
[ 56.849757]
[ 56.849757] stack backtrace:
[ 56.862194] CPU: 1 PID: 13 Comm: ksoftirqd/1 Not tainted 3.12.0-rc3+ #45
[ 56.868721] Hardware name: System manufacturer System Product Name/P8Z77 WS,
BIOS 3007 07/26/2012
[ 56.882004] ffffffff821944c0 ffff88080bbdb8c8 ffffffff8175a145
0000000000000007
[ 56.895630] ffff88080bbd5f40 ffff88080bbdb928 ffffffff81755b14
0000000000000001
[ 56.909313] ffff880800000001 ffff880800000000 ffffffff8101178f
0000000000000001
[ 56.923006] Call Trace:
[ 56.929532] [<ffffffff8175a145>] dump_stack+0x55/0x76
[ 56.936067] [<ffffffff81755b14>] print_usage_bug+0x1f7/0x208
[ 56.942445] [<ffffffff8101178f>] ? save_stack_trace+0x2f/0x50
[ 56.948932] [<ffffffff810cc0a0>] ? check_usage_backwards+0x150/0x150
[ 56.955470] [<ffffffff810ccb52>] mark_lock+0x282/0x2c0
[ 56.961945] [<ffffffff810ccfed>] __lock_acquire+0x45d/0x1d50
[ 56.968474] [<ffffffff810cce6e>] ? __lock_acquire+0x2de/0x1d50
[ 56.975140] [<ffffffff81393bf5>] ? cpumask_next_and+0x55/0x90
[ 56.981942] [<ffffffff810cef72>] lock_acquire+0x92/0x1d0
[ 56.988745] [<ffffffff8118f52a>] ? vm_unmap_aliases+0x16a/0x380
[ 56.995619] [<ffffffff817628f1>] _raw_spin_lock+0x41/0x50
[ 57.002493] [<ffffffff8118f52a>] ? vm_unmap_aliases+0x16a/0x380
[ 57.009447] [<ffffffff8118f52a>] vm_unmap_aliases+0x16a/0x380
[ 57.016477] [<ffffffff8118f44c>] ? vm_unmap_aliases+0x8c/0x380
[ 57.023607] [<ffffffff810436b0>] change_page_attr_set_clr+0xc0/0x460
[ 57.030818] [<ffffffff810cfb8d>] ? trace_hardirqs_on+0xd/0x10
[ 57.037896] [<ffffffff811a8330>] ? kmem_cache_free+0xb0/0x2b0
[ 57.044789] [<ffffffff811b59c3>] ? free_object_rcu+0x93/0xa0
[ 57.051720] [<ffffffff81043d9f>] set_memory_rw+0x2f/0x40
[ 57.058727] [<ffffffff8104e17c>] bpf_jit_free+0x2c/0x40
[ 57.065577] [<ffffffff81642cba>] sk_filter_release_rcu+0x1a/0x30
[ 57.072338] [<ffffffff811108e2>] rcu_process_callbacks+0x202/0x7c0
[ 57.078962] [<ffffffff81057f17>] __do_softirq+0xf7/0x3f0
[ 57.085373] [<ffffffff81058245>] run_ksoftirqd+0x35/0x70
cannot reuse jited filter memory, since it's readonly,
so use original bpf insns memory to hold work_struct
defer kfree of sk_filter until jit completed freeing
tested on x86_64 and i386
Signed-off-by: Alexei Starovoitov <a...@plumgrid.com>
---
arch/x86/net/bpf_jit_comp.c | 20 +++++++++++++++-----
include/linux/filter.h | 9 +++++++--
net/core/filter.c | 8 ++++++--
3 files changed, 28 insertions(+), 9 deletions(-)
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 79c216a..1396a0a 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -772,13 +772,23 @@ out:
return;
}
+static void bpf_jit_free_deferred(struct work_struct *work)
+{
+ struct sk_filter *fp = container_of((void *)work, struct sk_filter,
+ insns);
+ unsigned long addr = (unsigned long)fp->bpf_func & PAGE_MASK;
+ struct bpf_binary_header *header = (void *)addr;
+
+ set_memory_rw(addr, header->pages);
+ module_free(NULL, header);
+ kfree(fp);
+}
+
void bpf_jit_free(struct sk_filter *fp)
{
if (fp->bpf_func != sk_run_filter) {
- unsigned long addr = (unsigned long)fp->bpf_func & PAGE_MASK;
- struct bpf_binary_header *header = (void *)addr;
-
- set_memory_rw(addr, header->pages);
- module_free(NULL, header);
+ struct work_struct *work = (struct work_struct *)fp->insns;
+ INIT_WORK(work, bpf_jit_free_deferred);
+ schedule_work(work);
}
}
diff --git a/include/linux/filter.h b/include/linux/filter.h
index a6ac848..4876ac4 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -25,15 +25,20 @@ struct sk_filter
{
atomic_t refcnt;
unsigned int len; /* Number of filter blocks */
+ struct rcu_head rcu;
unsigned int (*bpf_func)(const struct sk_buff *skb,
const struct sock_filter *filter);
- struct rcu_head rcu;
+ /* insns start right after bpf_func, so that sk_run_filter() fetches
+ * first insn from the same cache line that was used to call into
+ * sk_run_filter()
+ */
struct sock_filter insns[0];
};
static inline unsigned int sk_filter_len(const struct sk_filter *fp)
{
- return fp->len * sizeof(struct sock_filter) + sizeof(*fp);
+ return max(fp->len * sizeof(struct sock_filter),
+ sizeof(struct work_struct)) + sizeof(*fp);
}
extern int sk_filter(struct sock *sk, struct sk_buff *skb);
diff --git a/net/core/filter.c b/net/core/filter.c
index 6438f29..1ebbc21 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -644,7 +644,9 @@ void sk_filter_release_rcu(struct rcu_head *rcu)
struct sk_filter *fp = container_of(rcu, struct sk_filter, rcu);
bpf_jit_free(fp);
+#if !defined(CONFIG_X86_64) /* x86_64 has a deferred free */
kfree(fp);
+#endif
}
EXPORT_SYMBOL(sk_filter_release_rcu);
@@ -676,7 +678,8 @@ int sk_unattached_filter_create(struct sk_filter **pfp,
struct sock_fprog *fprog)
{
struct sk_filter *fp;
- unsigned int fsize = sizeof(struct sock_filter) * fprog->len;
+ unsigned int fsize = max(sizeof(struct sock_filter) * fprog->len,
+ sizeof(struct work_struct));
int err;
/* Make sure new filter is there and in the right amounts. */
@@ -722,7 +725,8 @@ EXPORT_SYMBOL_GPL(sk_unattached_filter_destroy);
int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk)
{
struct sk_filter *fp, *old_fp;
- unsigned int fsize = sizeof(struct sock_filter) * fprog->len;
+ unsigned int fsize = max(sizeof(struct sock_filter) * fprog->len,
+ sizeof(struct work_struct));
int err;
if (sock_flag(sk, SOCK_FILTER_LOCKED))
--
1.7.9.5
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