Re: [PATCH] bpf: Call rcu_read_unlock() before copy_to_user()
On Thu, Jan 22, 2015 at 9:54 AM, Michael Holzheu wrote: >> > So call rcu_read_unlock() before copy_to_user(). We can >> > release the lock earlier because it is not needed for copy_to_user(). >> >> we cannot move the rcu unlock this way, since it protects the value. >> So we need to copy the value while still under rcu. > > Ok, right. I assume you will provide the correct fix. sure :) will do. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] bpf: Call rcu_read_unlock() before copy_to_user()
On Thu, 22 Jan 2015 09:27:21 -0800
Alexei Starovoitov wrote:
> On Thu, Jan 22, 2015 at 7:57 AM, Michael Holzheu
> wrote:
> > We must not hold locks when calling copy_to_user():
> >
> > BUG: sleeping function called from invalid context at mm/memory.c:3732
> > in_atomic(): 0, irqs_disabled(): 0, pid: 671, name: test_maps
> > 1 lock held by test_maps/671:
> > #0: (rcu_read_lock){..}, at: [<00264190>]
> > map_lookup_elem+0xe8/0x260
> > Preemption disabled at:[<001be3b6>] vprintk_default+0x56/0x68
> >
> > CPU: 0 PID: 671 Comm: test_maps Not tainted 3.19.0-rc5-00117-g5eb11d6-dirty
> > #424
> >1e447bb0 1e447c40 0002
> >1e447ce0 1e447c58 1e447c58 00115c8a
> > 00c08246 00c27e8a 000b
> >1e447ca0 1e447c40
> > 00115c8a 1e447c40 1e447ca0
> > Call Trace:
> > ([<00115b7e>] show_trace+0x12e/0x150)
> > [<00115c40>] show_stack+0xa0/0x100
> > [<009b163c>] dump_stack+0x74/0xc8
> > [<0017424a>] ___might_sleep+0x23a/0x248
> > [<002b58e8>] might_fault+0x70/0xe8
> > [<00264230>] map_lookup_elem+0x188/0x260
> > [<00264716>] SyS_bpf+0x20e/0x840
> > [<009bbe3a>] system_call+0xd6/0x24c
> > [<03fffd15f566>] 0x3fffd15f566
> > 1 lock held by test_maps/671:
> > #0: (rcu_read_lock){..}, at: [<00264190>]
> > map_lookup_elem+0xe8/0x260
> >
> > So call rcu_read_unlock() before copy_to_user(). We can
> > release the lock earlier because it is not needed for copy_to_user().
>
> we cannot move the rcu unlock this way, since it protects the value.
> So we need to copy the value while still under rcu.
Ok, right. I assume you will provide the correct fix.
> I'm puzzled how I missed this warning.
> I guess you have CONFIG_PREEMPT_RCU=y ?
Yes.
Regards,
Michael
--
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Re: [PATCH] bpf: Call rcu_read_unlock() before copy_to_user()
On Thu, Jan 22, 2015 at 7:57 AM, Michael Holzheu
wrote:
> We must not hold locks when calling copy_to_user():
>
> BUG: sleeping function called from invalid context at mm/memory.c:3732
> in_atomic(): 0, irqs_disabled(): 0, pid: 671, name: test_maps
> 1 lock held by test_maps/671:
> #0: (rcu_read_lock){..}, at: [<00264190>]
> map_lookup_elem+0xe8/0x260
> Preemption disabled at:[<001be3b6>] vprintk_default+0x56/0x68
>
> CPU: 0 PID: 671 Comm: test_maps Not tainted 3.19.0-rc5-00117-g5eb11d6-dirty
> #424
>1e447bb0 1e447c40 0002
>1e447ce0 1e447c58 1e447c58 00115c8a
> 00c08246 00c27e8a 000b
>1e447ca0 1e447c40
> 00115c8a 1e447c40 1e447ca0
> Call Trace:
> ([<00115b7e>] show_trace+0x12e/0x150)
> [<00115c40>] show_stack+0xa0/0x100
> [<009b163c>] dump_stack+0x74/0xc8
> [<0017424a>] ___might_sleep+0x23a/0x248
> [<002b58e8>] might_fault+0x70/0xe8
> [<00264230>] map_lookup_elem+0x188/0x260
> [<00264716>] SyS_bpf+0x20e/0x840
> [<009bbe3a>] system_call+0xd6/0x24c
> [<03fffd15f566>] 0x3fffd15f566
> 1 lock held by test_maps/671:
> #0: (rcu_read_lock){..}, at: [<00264190>]
> map_lookup_elem+0xe8/0x260
>
> So call rcu_read_unlock() before copy_to_user(). We can
> release the lock earlier because it is not needed for copy_to_user().
we cannot move the rcu unlock this way, since it protects the value.
So we need to copy the value while still under rcu.
I'm puzzled how I missed this warning.
I guess you have CONFIG_PREEMPT_RCU=y ?
and if (in_atomic()) return; as part of might_fault() hid it.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[PATCH] bpf: Call rcu_read_unlock() before copy_to_user()
We must not hold locks when calling copy_to_user():
BUG: sleeping function called from invalid context at mm/memory.c:3732
in_atomic(): 0, irqs_disabled(): 0, pid: 671, name: test_maps
1 lock held by test_maps/671:
#0: (rcu_read_lock){..}, at: [<00264190>]
map_lookup_elem+0xe8/0x260
Preemption disabled at:[<001be3b6>] vprintk_default+0x56/0x68
CPU: 0 PID: 671 Comm: test_maps Not tainted 3.19.0-rc5-00117-g5eb11d6-dirty #424
1e447bb0 1e447c40 0002
1e447ce0 1e447c58 1e447c58 00115c8a
00c08246 00c27e8a 000b
1e447ca0 1e447c40
00115c8a 1e447c40 1e447ca0
Call Trace:
([<00115b7e>] show_trace+0x12e/0x150)
[<00115c40>] show_stack+0xa0/0x100
[<009b163c>] dump_stack+0x74/0xc8
[<0017424a>] ___might_sleep+0x23a/0x248
[<002b58e8>] might_fault+0x70/0xe8
[<00264230>] map_lookup_elem+0x188/0x260
[<00264716>] SyS_bpf+0x20e/0x840
[<009bbe3a>] system_call+0xd6/0x24c
[<03fffd15f566>] 0x3fffd15f566
1 lock held by test_maps/671:
#0: (rcu_read_lock){..}, at: [<00264190>]
map_lookup_elem+0xe8/0x260
So call rcu_read_unlock() before copy_to_user(). We can
release the lock earlier because it is not needed for copy_to_user().
Signed-off-by: Michael Holzheu
---
kernel/bpf/syscall.c |7 +++
1 file changed, 3 insertions(+), 4 deletions(-)
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -172,17 +172,16 @@ static int map_lookup_elem(union bpf_att
err = -ENOENT;
rcu_read_lock();
value = map->ops->map_lookup_elem(map, key);
+ rcu_read_unlock();
if (!value)
- goto err_unlock;
+ goto free_key;
err = -EFAULT;
if (copy_to_user(uvalue, value, map->value_size) != 0)
- goto err_unlock;
+ goto free_key;
err = 0;
-err_unlock:
- rcu_read_unlock();
free_key:
kfree(key);
err_put:
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[PATCH] bpf: Call rcu_read_unlock() before copy_to_user()
We must not hold locks when calling copy_to_user():
BUG: sleeping function called from invalid context at mm/memory.c:3732
in_atomic(): 0, irqs_disabled(): 0, pid: 671, name: test_maps
1 lock held by test_maps/671:
#0: (rcu_read_lock){..}, at: [00264190]
map_lookup_elem+0xe8/0x260
Preemption disabled at:[001be3b6] vprintk_default+0x56/0x68
CPU: 0 PID: 671 Comm: test_maps Not tainted 3.19.0-rc5-00117-g5eb11d6-dirty #424
1e447bb0 1e447c40 0002
1e447ce0 1e447c58 1e447c58 00115c8a
00c08246 00c27e8a 000b
1e447ca0 1e447c40
00115c8a 1e447c40 1e447ca0
Call Trace:
([00115b7e] show_trace+0x12e/0x150)
[00115c40] show_stack+0xa0/0x100
[009b163c] dump_stack+0x74/0xc8
[0017424a] ___might_sleep+0x23a/0x248
[002b58e8] might_fault+0x70/0xe8
[00264230] map_lookup_elem+0x188/0x260
[00264716] SyS_bpf+0x20e/0x840
[009bbe3a] system_call+0xd6/0x24c
[03fffd15f566] 0x3fffd15f566
1 lock held by test_maps/671:
#0: (rcu_read_lock){..}, at: [00264190]
map_lookup_elem+0xe8/0x260
So call rcu_read_unlock() before copy_to_user(). We can
release the lock earlier because it is not needed for copy_to_user().
Signed-off-by: Michael Holzheu holz...@linux.vnet.ibm.com
---
kernel/bpf/syscall.c |7 +++
1 file changed, 3 insertions(+), 4 deletions(-)
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -172,17 +172,16 @@ static int map_lookup_elem(union bpf_att
err = -ENOENT;
rcu_read_lock();
value = map-ops-map_lookup_elem(map, key);
+ rcu_read_unlock();
if (!value)
- goto err_unlock;
+ goto free_key;
err = -EFAULT;
if (copy_to_user(uvalue, value, map-value_size) != 0)
- goto err_unlock;
+ goto free_key;
err = 0;
-err_unlock:
- rcu_read_unlock();
free_key:
kfree(key);
err_put:
--
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] bpf: Call rcu_read_unlock() before copy_to_user()
On Thu, Jan 22, 2015 at 9:54 AM, Michael Holzheu holz...@linux.vnet.ibm.com wrote: So call rcu_read_unlock() before copy_to_user(). We can release the lock earlier because it is not needed for copy_to_user(). we cannot move the rcu unlock this way, since it protects the value. So we need to copy the value while still under rcu. Ok, right. I assume you will provide the correct fix. sure :) will do. -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] bpf: Call rcu_read_unlock() before copy_to_user()
On Thu, 22 Jan 2015 09:27:21 -0800
Alexei Starovoitov alexei.starovoi...@gmail.com wrote:
On Thu, Jan 22, 2015 at 7:57 AM, Michael Holzheu
holz...@linux.vnet.ibm.com wrote:
We must not hold locks when calling copy_to_user():
BUG: sleeping function called from invalid context at mm/memory.c:3732
in_atomic(): 0, irqs_disabled(): 0, pid: 671, name: test_maps
1 lock held by test_maps/671:
#0: (rcu_read_lock){..}, at: [00264190]
map_lookup_elem+0xe8/0x260
Preemption disabled at:[001be3b6] vprintk_default+0x56/0x68
CPU: 0 PID: 671 Comm: test_maps Not tainted 3.19.0-rc5-00117-g5eb11d6-dirty
#424
1e447bb0 1e447c40 0002
1e447ce0 1e447c58 1e447c58 00115c8a
00c08246 00c27e8a 000b
1e447ca0 1e447c40
00115c8a 1e447c40 1e447ca0
Call Trace:
([00115b7e] show_trace+0x12e/0x150)
[00115c40] show_stack+0xa0/0x100
[009b163c] dump_stack+0x74/0xc8
[0017424a] ___might_sleep+0x23a/0x248
[002b58e8] might_fault+0x70/0xe8
[00264230] map_lookup_elem+0x188/0x260
[00264716] SyS_bpf+0x20e/0x840
[009bbe3a] system_call+0xd6/0x24c
[03fffd15f566] 0x3fffd15f566
1 lock held by test_maps/671:
#0: (rcu_read_lock){..}, at: [00264190]
map_lookup_elem+0xe8/0x260
So call rcu_read_unlock() before copy_to_user(). We can
release the lock earlier because it is not needed for copy_to_user().
we cannot move the rcu unlock this way, since it protects the value.
So we need to copy the value while still under rcu.
Ok, right. I assume you will provide the correct fix.
I'm puzzled how I missed this warning.
I guess you have CONFIG_PREEMPT_RCU=y ?
Yes.
Regards,
Michael
--
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] bpf: Call rcu_read_unlock() before copy_to_user()
On Thu, Jan 22, 2015 at 7:57 AM, Michael Holzheu
holz...@linux.vnet.ibm.com wrote:
We must not hold locks when calling copy_to_user():
BUG: sleeping function called from invalid context at mm/memory.c:3732
in_atomic(): 0, irqs_disabled(): 0, pid: 671, name: test_maps
1 lock held by test_maps/671:
#0: (rcu_read_lock){..}, at: [00264190]
map_lookup_elem+0xe8/0x260
Preemption disabled at:[001be3b6] vprintk_default+0x56/0x68
CPU: 0 PID: 671 Comm: test_maps Not tainted 3.19.0-rc5-00117-g5eb11d6-dirty
#424
1e447bb0 1e447c40 0002
1e447ce0 1e447c58 1e447c58 00115c8a
00c08246 00c27e8a 000b
1e447ca0 1e447c40
00115c8a 1e447c40 1e447ca0
Call Trace:
([00115b7e] show_trace+0x12e/0x150)
[00115c40] show_stack+0xa0/0x100
[009b163c] dump_stack+0x74/0xc8
[0017424a] ___might_sleep+0x23a/0x248
[002b58e8] might_fault+0x70/0xe8
[00264230] map_lookup_elem+0x188/0x260
[00264716] SyS_bpf+0x20e/0x840
[009bbe3a] system_call+0xd6/0x24c
[03fffd15f566] 0x3fffd15f566
1 lock held by test_maps/671:
#0: (rcu_read_lock){..}, at: [00264190]
map_lookup_elem+0xe8/0x260
So call rcu_read_unlock() before copy_to_user(). We can
release the lock earlier because it is not needed for copy_to_user().
we cannot move the rcu unlock this way, since it protects the value.
So we need to copy the value while still under rcu.
I'm puzzled how I missed this warning.
I guess you have CONFIG_PREEMPT_RCU=y ?
and if (in_atomic()) return; as part of might_fault() hid it.
--
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
