* [PATCH bpf v3] bpf/tracing: fix a deadlock in perf_event_detach_bpf_prog
@ 2018-04-10 7:21 Yonghong Song
2018-04-10 8:54 ` Daniel Borkmann
0 siblings, 1 reply; 3+ messages in thread
From: Yonghong Song @ 2018-04-10 7:21 UTC (permalink / raw)
To: ast, daniel, netdev; +Cc: kernel-team
syzbot reported a possible deadlock in perf_event_detach_bpf_prog.
The error details:
======================================================
WARNING: possible circular locking dependency detected
4.16.0-rc7+ #3 Not tainted
------------------------------------------------------
syz-executor7/24531 is trying to acquire lock:
(bpf_event_mutex){+.+.}, at: [<000000008a849b07>] perf_event_detach_bpf_prog+0x92/0x3d0 kernel/trace/bpf_trace.c:854
but task is already holding lock:
(&mm->mmap_sem){++++}, at: [<0000000038768f87>] vm_mmap_pgoff+0x198/0x280 mm/util.c:353
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (&mm->mmap_sem){++++}:
__might_fault+0x13a/0x1d0 mm/memory.c:4571
_copy_to_user+0x2c/0xc0 lib/usercopy.c:25
copy_to_user include/linux/uaccess.h:155 [inline]
bpf_prog_array_copy_info+0xf2/0x1c0 kernel/bpf/core.c:1694
perf_event_query_prog_array+0x1c7/0x2c0 kernel/trace/bpf_trace.c:891
_perf_ioctl kernel/events/core.c:4750 [inline]
perf_ioctl+0x3e1/0x1480 kernel/events/core.c:4770
vfs_ioctl fs/ioctl.c:46 [inline]
do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686
SYSC_ioctl fs/ioctl.c:701 [inline]
SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x42/0xb7
-> #0 (bpf_event_mutex){+.+.}:
lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:3920
__mutex_lock_common kernel/locking/mutex.c:756 [inline]
__mutex_lock+0x16f/0x1a80 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
perf_event_detach_bpf_prog+0x92/0x3d0 kernel/trace/bpf_trace.c:854
perf_event_free_bpf_prog kernel/events/core.c:8147 [inline]
_free_event+0xbdb/0x10f0 kernel/events/core.c:4116
put_event+0x24/0x30 kernel/events/core.c:4204
perf_mmap_close+0x60d/0x1010 kernel/events/core.c:5172
remove_vma+0xb4/0x1b0 mm/mmap.c:172
remove_vma_list mm/mmap.c:2490 [inline]
do_munmap+0x82a/0xdf0 mm/mmap.c:2731
mmap_region+0x59e/0x15a0 mm/mmap.c:1646
do_mmap+0x6c0/0xe00 mm/mmap.c:1483
do_mmap_pgoff include/linux/mm.h:2223 [inline]
vm_mmap_pgoff+0x1de/0x280 mm/util.c:355
SYSC_mmap_pgoff mm/mmap.c:1533 [inline]
SyS_mmap_pgoff+0x462/0x5f0 mm/mmap.c:1491
SYSC_mmap arch/x86/kernel/sys_x86_64.c:100 [inline]
SyS_mmap+0x16/0x20 arch/x86/kernel/sys_x86_64.c:91
do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x42/0xb7
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&mm->mmap_sem);
lock(bpf_event_mutex);
lock(&mm->mmap_sem);
lock(bpf_event_mutex);
*** DEADLOCK ***
======================================================
The bug is introduced by Commit f371b304f12e ("bpf/tracing: allow
user space to query prog array on the same tp") where copy_to_user,
which requires mm->mmap_sem, is called inside bpf_event_mutex lock.
At the same time, during perf_event file descriptor close,
mm->mmap_sem is held first and then subsequent
perf_event_detach_bpf_prog needs bpf_event_mutex lock.
Such a senario caused a deadlock.
As suggested by Danial, moving copy_to_user out of the
bpf_event_mutex lock should fix the problem.
Fixes: f371b304f12e ("bpf/tracing: allow user space to query prog array on the same tp")
Reported-by: syzbot+dc5ca0e4c9bfafaf2bae@syzkaller.appspotmail.com
Signed-off-by: Yonghong Song <yhs@fb.com>
---
include/linux/bpf.h | 4 ++--
kernel/bpf/core.c | 45 +++++++++++++++++++++++++++++----------------
kernel/trace/bpf_trace.c | 19 +++++++++++++++----
3 files changed, 46 insertions(+), 22 deletions(-)
Changelog:
v2 -> v3:
. Remove the redundant label in function perf_event_query_prog_array.
v1 -> v2:
. Use the common core function for prog_id copying for two
different prog_array copy routines, suggested by Alexei.
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 95a7abd..486e65e 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -339,8 +339,8 @@ int bpf_prog_array_copy_to_user(struct bpf_prog_array __rcu *progs,
void bpf_prog_array_delete_safe(struct bpf_prog_array __rcu *progs,
struct bpf_prog *old_prog);
int bpf_prog_array_copy_info(struct bpf_prog_array __rcu *array,
- __u32 __user *prog_ids, u32 request_cnt,
- __u32 __user *prog_cnt);
+ u32 *prog_ids, u32 request_cnt,
+ u32 *prog_cnt);
int bpf_prog_array_copy(struct bpf_prog_array __rcu *old_array,
struct bpf_prog *exclude_prog,
struct bpf_prog *include_prog,
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index d315b39..ba03ec3 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -1572,13 +1572,32 @@ int bpf_prog_array_length(struct bpf_prog_array __rcu *progs)
return cnt;
}
+static bool bpf_prog_array_copy_core(struct bpf_prog **prog,
+ u32 *prog_ids,
+ u32 request_cnt)
+{
+ int i = 0;
+
+ for (; *prog; prog++) {
+ if (*prog == &dummy_bpf_prog.prog)
+ continue;
+ prog_ids[i] = (*prog)->aux->id;
+ if (++i == request_cnt) {
+ prog++;
+ break;
+ }
+ }
+
+ return !!(*prog);
+}
+
int bpf_prog_array_copy_to_user(struct bpf_prog_array __rcu *progs,
__u32 __user *prog_ids, u32 cnt)
{
struct bpf_prog **prog;
unsigned long err = 0;
- u32 i = 0, *ids;
bool nospc;
+ u32 *ids;
/* users of this function are doing:
* cnt = bpf_prog_array_length();
@@ -1595,16 +1614,7 @@ int bpf_prog_array_copy_to_user(struct bpf_prog_array __rcu *progs,
return -ENOMEM;
rcu_read_lock();
prog = rcu_dereference(progs)->progs;
- for (; *prog; prog++) {
- if (*prog == &dummy_bpf_prog.prog)
- continue;
- ids[i] = (*prog)->aux->id;
- if (++i == cnt) {
- prog++;
- break;
- }
- }
- nospc = !!(*prog);
+ nospc = bpf_prog_array_copy_core(prog, ids, cnt);
rcu_read_unlock();
err = copy_to_user(prog_ids, ids, cnt * sizeof(u32));
kfree(ids);
@@ -1683,22 +1693,25 @@ int bpf_prog_array_copy(struct bpf_prog_array __rcu *old_array,
}
int bpf_prog_array_copy_info(struct bpf_prog_array __rcu *array,
- __u32 __user *prog_ids, u32 request_cnt,
- __u32 __user *prog_cnt)
+ u32 *prog_ids, u32 request_cnt,
+ u32 *prog_cnt)
{
+ struct bpf_prog **prog;
u32 cnt = 0;
if (array)
cnt = bpf_prog_array_length(array);
- if (copy_to_user(prog_cnt, &cnt, sizeof(cnt)))
- return -EFAULT;
+ *prog_cnt = cnt;
/* return early if user requested only program count or nothing to copy */
if (!request_cnt || !cnt)
return 0;
- return bpf_prog_array_copy_to_user(array, prog_ids, request_cnt);
+ /* this function is called under trace/bpf_trace.c: bpf_event_mutex */
+ prog = rcu_dereference_check(array, 1)->progs;
+ return bpf_prog_array_copy_core(prog, prog_ids, request_cnt) ? -ENOSPC
+ : 0;
}
static void bpf_prog_free_deferred(struct work_struct *work)
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index d88e96d..f505d43 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -977,6 +977,7 @@ int perf_event_query_prog_array(struct perf_event *event, void __user *info)
{
struct perf_event_query_bpf __user *uquery = info;
struct perf_event_query_bpf query = {};
+ u32 *ids, prog_cnt, ids_len;
int ret;
if (!capable(CAP_SYS_ADMIN))
@@ -985,16 +986,26 @@ int perf_event_query_prog_array(struct perf_event *event, void __user *info)
return -EINVAL;
if (copy_from_user(&query, uquery, sizeof(query)))
return -EFAULT;
- if (query.ids_len > BPF_TRACE_MAX_PROGS)
+
+ ids_len = query.ids_len;
+ if (ids_len > BPF_TRACE_MAX_PROGS)
return -E2BIG;
+ ids = kcalloc(ids_len, sizeof(u32), GFP_USER | __GFP_NOWARN);
+ if (!ids)
+ return -ENOMEM;
mutex_lock(&bpf_event_mutex);
ret = bpf_prog_array_copy_info(event->tp_event->prog_array,
- uquery->ids,
- query.ids_len,
- &uquery->prog_cnt);
+ ids,
+ ids_len,
+ &prog_cnt);
mutex_unlock(&bpf_event_mutex);
+ if (copy_to_user(&uquery->prog_cnt, &prog_cnt, sizeof(prog_cnt)) ||
+ copy_to_user(uquery->ids, ids, ids_len * sizeof(u32)))
+ ret = -EFAULT;
+
+ kfree(ids);
return ret;
}
--
2.9.5
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH bpf v3] bpf/tracing: fix a deadlock in perf_event_detach_bpf_prog
2018-04-10 7:21 [PATCH bpf v3] bpf/tracing: fix a deadlock in perf_event_detach_bpf_prog Yonghong Song
@ 2018-04-10 8:54 ` Daniel Borkmann
2018-04-10 16:04 ` Yonghong Song
0 siblings, 1 reply; 3+ messages in thread
From: Daniel Borkmann @ 2018-04-10 8:54 UTC (permalink / raw)
To: Yonghong Song, ast, netdev; +Cc: kernel-team
On 04/10/2018 09:21 AM, Yonghong Song wrote:
> syzbot reported a possible deadlock in perf_event_detach_bpf_prog.
> The error details:
> ======================================================
> WARNING: possible circular locking dependency detected
> 4.16.0-rc7+ #3 Not tainted
> ------------------------------------------------------
> syz-executor7/24531 is trying to acquire lock:
> (bpf_event_mutex){+.+.}, at: [<000000008a849b07>] perf_event_detach_bpf_prog+0x92/0x3d0 kernel/trace/bpf_trace.c:854
>
> but task is already holding lock:
> (&mm->mmap_sem){++++}, at: [<0000000038768f87>] vm_mmap_pgoff+0x198/0x280 mm/util.c:353
>
> which lock already depends on the new lock.
>
> the existing dependency chain (in reverse order) is:
>
> -> #1 (&mm->mmap_sem){++++}:
> __might_fault+0x13a/0x1d0 mm/memory.c:4571
> _copy_to_user+0x2c/0xc0 lib/usercopy.c:25
> copy_to_user include/linux/uaccess.h:155 [inline]
> bpf_prog_array_copy_info+0xf2/0x1c0 kernel/bpf/core.c:1694
> perf_event_query_prog_array+0x1c7/0x2c0 kernel/trace/bpf_trace.c:891
> _perf_ioctl kernel/events/core.c:4750 [inline]
> perf_ioctl+0x3e1/0x1480 kernel/events/core.c:4770
> vfs_ioctl fs/ioctl.c:46 [inline]
> do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686
> SYSC_ioctl fs/ioctl.c:701 [inline]
> SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
> do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
> entry_SYSCALL_64_after_hwframe+0x42/0xb7
>
> -> #0 (bpf_event_mutex){+.+.}:
> lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:3920
> __mutex_lock_common kernel/locking/mutex.c:756 [inline]
> __mutex_lock+0x16f/0x1a80 kernel/locking/mutex.c:893
> mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
> perf_event_detach_bpf_prog+0x92/0x3d0 kernel/trace/bpf_trace.c:854
> perf_event_free_bpf_prog kernel/events/core.c:8147 [inline]
> _free_event+0xbdb/0x10f0 kernel/events/core.c:4116
> put_event+0x24/0x30 kernel/events/core.c:4204
> perf_mmap_close+0x60d/0x1010 kernel/events/core.c:5172
> remove_vma+0xb4/0x1b0 mm/mmap.c:172
> remove_vma_list mm/mmap.c:2490 [inline]
> do_munmap+0x82a/0xdf0 mm/mmap.c:2731
> mmap_region+0x59e/0x15a0 mm/mmap.c:1646
> do_mmap+0x6c0/0xe00 mm/mmap.c:1483
> do_mmap_pgoff include/linux/mm.h:2223 [inline]
> vm_mmap_pgoff+0x1de/0x280 mm/util.c:355
> SYSC_mmap_pgoff mm/mmap.c:1533 [inline]
> SyS_mmap_pgoff+0x462/0x5f0 mm/mmap.c:1491
> SYSC_mmap arch/x86/kernel/sys_x86_64.c:100 [inline]
> SyS_mmap+0x16/0x20 arch/x86/kernel/sys_x86_64.c:91
> do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
> entry_SYSCALL_64_after_hwframe+0x42/0xb7
>
> other info that might help us debug this:
>
> Possible unsafe locking scenario:
>
> CPU0 CPU1
> ---- ----
> lock(&mm->mmap_sem);
> lock(bpf_event_mutex);
> lock(&mm->mmap_sem);
> lock(bpf_event_mutex);
>
> *** DEADLOCK ***
> ======================================================
>
> The bug is introduced by Commit f371b304f12e ("bpf/tracing: allow
> user space to query prog array on the same tp") where copy_to_user,
> which requires mm->mmap_sem, is called inside bpf_event_mutex lock.
> At the same time, during perf_event file descriptor close,
> mm->mmap_sem is held first and then subsequent
> perf_event_detach_bpf_prog needs bpf_event_mutex lock.
> Such a senario caused a deadlock.
>
> As suggested by Danial, moving copy_to_user out of the
Nit: typo :)
> bpf_event_mutex lock should fix the problem.
>
> Fixes: f371b304f12e ("bpf/tracing: allow user space to query prog array on the same tp")
> Reported-by: syzbot+dc5ca0e4c9bfafaf2bae@syzkaller.appspotmail.com
> Signed-off-by: Yonghong Song <yhs@fb.com>
> ---
> include/linux/bpf.h | 4 ++--
> kernel/bpf/core.c | 45 +++++++++++++++++++++++++++++----------------
> kernel/trace/bpf_trace.c | 19 +++++++++++++++----
> 3 files changed, 46 insertions(+), 22 deletions(-)
>
> Changelog:
> v2 -> v3:
> . Remove the redundant label in function perf_event_query_prog_array.
> v1 -> v2:
> . Use the common core function for prog_id copying for two
> different prog_array copy routines, suggested by Alexei.
>
[...]
> static void bpf_prog_free_deferred(struct work_struct *work)
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index d88e96d..f505d43 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -977,6 +977,7 @@ int perf_event_query_prog_array(struct perf_event *event, void __user *info)
> {
> struct perf_event_query_bpf __user *uquery = info;
> struct perf_event_query_bpf query = {};
> + u32 *ids, prog_cnt, ids_len;
> int ret;
>
> if (!capable(CAP_SYS_ADMIN))
> @@ -985,16 +986,26 @@ int perf_event_query_prog_array(struct perf_event *event, void __user *info)
> return -EINVAL;
> if (copy_from_user(&query, uquery, sizeof(query)))
> return -EFAULT;
> - if (query.ids_len > BPF_TRACE_MAX_PROGS)
> +
> + ids_len = query.ids_len;
> + if (ids_len > BPF_TRACE_MAX_PROGS)
> return -E2BIG;
> + ids = kcalloc(ids_len, sizeof(u32), GFP_USER | __GFP_NOWARN);
> + if (!ids)
> + return -ENOMEM;
Fix looks good to me, but could you still add a comment stating that we don't
need to check for ZERO_SIZE_PTR above since we handle this gracefully in the
bpf_prog_array_copy_info() plus it's also required for the case where the user
only wants to check for the uquery->prog_cnt, but nothing else.
> mutex_lock(&bpf_event_mutex);
> ret = bpf_prog_array_copy_info(event->tp_event->prog_array,
> - uquery->ids,
> - query.ids_len,
> - &uquery->prog_cnt);
> + ids,
> + ids_len,
> + &prog_cnt);
> mutex_unlock(&bpf_event_mutex);
>
> + if (copy_to_user(&uquery->prog_cnt, &prog_cnt, sizeof(prog_cnt)) ||
> + copy_to_user(uquery->ids, ids, ids_len * sizeof(u32)))
> + ret = -EFAULT;
> +
> + kfree(ids);
> return ret;
> }
Thanks,
Daniel
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH bpf v3] bpf/tracing: fix a deadlock in perf_event_detach_bpf_prog
2018-04-10 8:54 ` Daniel Borkmann
@ 2018-04-10 16:04 ` Yonghong Song
0 siblings, 0 replies; 3+ messages in thread
From: Yonghong Song @ 2018-04-10 16:04 UTC (permalink / raw)
To: Daniel Borkmann, ast, netdev; +Cc: kernel-team
On 4/10/18 1:54 AM, Daniel Borkmann wrote:
> On 04/10/2018 09:21 AM, Yonghong Song wrote:
>> syzbot reported a possible deadlock in perf_event_detach_bpf_prog.
>> The error details:
>> ======================================================
>> WARNING: possible circular locking dependency detected
>> 4.16.0-rc7+ #3 Not tainted
>> ------------------------------------------------------
>> syz-executor7/24531 is trying to acquire lock:
>> (bpf_event_mutex){+.+.}, at: [<000000008a849b07>] perf_event_detach_bpf_prog+0x92/0x3d0 kernel/trace/bpf_trace.c:854
>>
>> but task is already holding lock:
>> (&mm->mmap_sem){++++}, at: [<0000000038768f87>] vm_mmap_pgoff+0x198/0x280 mm/util.c:353
>>
>> which lock already depends on the new lock.
>>
>> the existing dependency chain (in reverse order) is:
>>
>> -> #1 (&mm->mmap_sem){++++}:
>> __might_fault+0x13a/0x1d0 mm/memory.c:4571
>> _copy_to_user+0x2c/0xc0 lib/usercopy.c:25
>> copy_to_user include/linux/uaccess.h:155 [inline]
>> bpf_prog_array_copy_info+0xf2/0x1c0 kernel/bpf/core.c:1694
>> perf_event_query_prog_array+0x1c7/0x2c0 kernel/trace/bpf_trace.c:891
>> _perf_ioctl kernel/events/core.c:4750 [inline]
>> perf_ioctl+0x3e1/0x1480 kernel/events/core.c:4770
>> vfs_ioctl fs/ioctl.c:46 [inline]
>> do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686
>> SYSC_ioctl fs/ioctl.c:701 [inline]
>> SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
>> do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
>> entry_SYSCALL_64_after_hwframe+0x42/0xb7
>>
>> -> #0 (bpf_event_mutex){+.+.}:
>> lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:3920
>> __mutex_lock_common kernel/locking/mutex.c:756 [inline]
>> __mutex_lock+0x16f/0x1a80 kernel/locking/mutex.c:893
>> mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
>> perf_event_detach_bpf_prog+0x92/0x3d0 kernel/trace/bpf_trace.c:854
>> perf_event_free_bpf_prog kernel/events/core.c:8147 [inline]
>> _free_event+0xbdb/0x10f0 kernel/events/core.c:4116
>> put_event+0x24/0x30 kernel/events/core.c:4204
>> perf_mmap_close+0x60d/0x1010 kernel/events/core.c:5172
>> remove_vma+0xb4/0x1b0 mm/mmap.c:172
>> remove_vma_list mm/mmap.c:2490 [inline]
>> do_munmap+0x82a/0xdf0 mm/mmap.c:2731
>> mmap_region+0x59e/0x15a0 mm/mmap.c:1646
>> do_mmap+0x6c0/0xe00 mm/mmap.c:1483
>> do_mmap_pgoff include/linux/mm.h:2223 [inline]
>> vm_mmap_pgoff+0x1de/0x280 mm/util.c:355
>> SYSC_mmap_pgoff mm/mmap.c:1533 [inline]
>> SyS_mmap_pgoff+0x462/0x5f0 mm/mmap.c:1491
>> SYSC_mmap arch/x86/kernel/sys_x86_64.c:100 [inline]
>> SyS_mmap+0x16/0x20 arch/x86/kernel/sys_x86_64.c:91
>> do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
>> entry_SYSCALL_64_after_hwframe+0x42/0xb7
>>
>> other info that might help us debug this:
>>
>> Possible unsafe locking scenario:
>>
>> CPU0 CPU1
>> ---- ----
>> lock(&mm->mmap_sem);
>> lock(bpf_event_mutex);
>> lock(&mm->mmap_sem);
>> lock(bpf_event_mutex);
>>
>> *** DEADLOCK ***
>> ======================================================
>>
>> The bug is introduced by Commit f371b304f12e ("bpf/tracing: allow
>> user space to query prog array on the same tp") where copy_to_user,
>> which requires mm->mmap_sem, is called inside bpf_event_mutex lock.
>> At the same time, during perf_event file descriptor close,
>> mm->mmap_sem is held first and then subsequent
>> perf_event_detach_bpf_prog needs bpf_event_mutex lock.
>> Such a senario caused a deadlock.
>>
>> As suggested by Danial, moving copy_to_user out of the
>
> Nit: typo :)
Oh, my bad. will correct.
>
>> bpf_event_mutex lock should fix the problem.
>>
>> Fixes: f371b304f12e ("bpf/tracing: allow user space to query prog array on the same tp")
>> Reported-by: syzbot+dc5ca0e4c9bfafaf2bae@syzkaller.appspotmail.com
>> Signed-off-by: Yonghong Song <yhs@fb.com>
>> ---
>> include/linux/bpf.h | 4 ++--
>> kernel/bpf/core.c | 45 +++++++++++++++++++++++++++++----------------
>> kernel/trace/bpf_trace.c | 19 +++++++++++++++----
>> 3 files changed, 46 insertions(+), 22 deletions(-)
>>
>> Changelog:
>> v2 -> v3:
>> . Remove the redundant label in function perf_event_query_prog_array.
>> v1 -> v2:
>> . Use the common core function for prog_id copying for two
>> different prog_array copy routines, suggested by Alexei.
>>
> [...]
>> static void bpf_prog_free_deferred(struct work_struct *work)
>> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
>> index d88e96d..f505d43 100644
>> --- a/kernel/trace/bpf_trace.c
>> +++ b/kernel/trace/bpf_trace.c
>> @@ -977,6 +977,7 @@ int perf_event_query_prog_array(struct perf_event *event, void __user *info)
>> {
>> struct perf_event_query_bpf __user *uquery = info;
>> struct perf_event_query_bpf query = {};
>> + u32 *ids, prog_cnt, ids_len;
>> int ret;
>>
>> if (!capable(CAP_SYS_ADMIN))
>> @@ -985,16 +986,26 @@ int perf_event_query_prog_array(struct perf_event *event, void __user *info)
>> return -EINVAL;
>> if (copy_from_user(&query, uquery, sizeof(query)))
>> return -EFAULT;
>> - if (query.ids_len > BPF_TRACE_MAX_PROGS)
>> +
>> + ids_len = query.ids_len;
>> + if (ids_len > BPF_TRACE_MAX_PROGS)
>> return -E2BIG;
>> + ids = kcalloc(ids_len, sizeof(u32), GFP_USER | __GFP_NOWARN);
>> + if (!ids)
>> + return -ENOMEM;
>
> Fix looks good to me, but could you still add a comment stating that we don't
> need to check for ZERO_SIZE_PTR above since we handle this gracefully in the
> bpf_prog_array_copy_info() plus it's also required for the case where the user
> only wants to check for the uquery->prog_cnt, but nothing else.
Will add the comment and send another version.
Thanks.
>
>> mutex_lock(&bpf_event_mutex);
>> ret = bpf_prog_array_copy_info(event->tp_event->prog_array,
>> - uquery->ids,
>> - query.ids_len,
>> - &uquery->prog_cnt);
>> + ids,
>> + ids_len,
>> + &prog_cnt);
>> mutex_unlock(&bpf_event_mutex);
>>
>> + if (copy_to_user(&uquery->prog_cnt, &prog_cnt, sizeof(prog_cnt)) ||
>> + copy_to_user(uquery->ids, ids, ids_len * sizeof(u32)))
>> + ret = -EFAULT;
>> +
>> + kfree(ids);
>> return ret;
>> }
>
> Thanks,
> Daniel
>
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2018-04-10 16:05 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2018-04-10 7:21 [PATCH bpf v3] bpf/tracing: fix a deadlock in perf_event_detach_bpf_prog Yonghong Song
2018-04-10 8:54 ` Daniel Borkmann
2018-04-10 16:04 ` Yonghong Song
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