LinuxLists.cc - [PATCH] audit, io_uring, io-wq: Fix memory leak in io_sq_thread() and io_wqe

2022-08-03 05:48:50

Subject: [PATCH] audit, io_uring, io-wq: Fix memory leak in io_sq_thread() and io_wqe_worker()

2022-08-03 13:35:04

Subject: Re: [PATCH] audit, io_uring, io-wq: Fix memory leak in io_sq_thread() and io_wqe_worker()

On Wed, Aug 3, 2022 at 1:03 AM Peilin Ye <[email protected]> wrote:
>
> From: Peilin Ye <[email protected]>
>
> Currently @audit_context is allocated twice for io_uring workers:
>
> 1. copy_process() calls audit_alloc();
> 2. io_sq_thread() or io_wqe_worker() calls audit_alloc_kernel() (which
> is effectively audit_alloc()) and overwrites @audit_context,
> causing:
>
> BUG: memory leak
> unreferenced object 0xffff888144547400 (size 1024):
> <...>
> hex dump (first 32 bytes):
> 00 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00 ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> backtrace:
> [<ffffffff8135cfc3>] audit_alloc+0x133/0x210
> [<ffffffff81239e63>] copy_process+0xcd3/0x2340
> [<ffffffff8123b5f3>] create_io_thread+0x63/0x90
> [<ffffffff81686604>] create_io_worker+0xb4/0x230
> [<ffffffff81686f68>] io_wqe_enqueue+0x248/0x3b0
> [<ffffffff8167663a>] io_queue_iowq+0xba/0x200
> [<ffffffff816768b3>] io_queue_async+0x113/0x180
> [<ffffffff816840df>] io_req_task_submit+0x18f/0x1a0
> [<ffffffff816841cd>] io_apoll_task_func+0xdd/0x120
> [<ffffffff8167d49f>] tctx_task_work+0x11f/0x570
> [<ffffffff81272c4e>] task_work_run+0x7e/0xc0
> [<ffffffff8125a688>] get_signal+0xc18/0xf10
> [<ffffffff8111645b>] arch_do_signal_or_restart+0x2b/0x730
> [<ffffffff812ea44e>] exit_to_user_mode_prepare+0x5e/0x180
> [<ffffffff844ae1b2>] syscall_exit_to_user_mode+0x12/0x20
> [<ffffffff844a7e80>] do_syscall_64+0x40/0x80
>
> Then,
>
> 3. io_sq_thread() or io_wqe_worker() frees @audit_context using
> audit_free();
> 4. do_exit() eventually calls audit_free() again, which is okay
> because audit_free() does a NULL check.
>
> Free the old @audit_context first in audit_alloc_kernel(), and delete
> the redundant calls to audit_free() for less confusion.
>
> Fixes: 5bd2182d58e9 ("audit,io_uring,io-wq: add some basic audit support to io_uring")
> Cc: [email protected]
> Signed-off-by: Peilin Ye <[email protected]>
> ---
> Hi all,
>
> A better way to fix this memleak would probably be checking
> @args->io_thread in copy_process()? Something like:
>
> if (args->io_thread)
> retval = audit_alloc_kernel();
> else
> retval = audit_alloc();
>
> But I didn't want to add another if to copy_process() for this bugfix.
> Please suggest, thanks!

Thanks for the report and patch! I'll take a closer look at this
today and get back to you.

> fs/io-wq.c | 1 -
> fs/io_uring.c | 2 --
> kernel/auditsc.c | 1 +
> 3 files changed, 1 insertion(+), 3 deletions(-)

--
paul-moore.com

2022-08-03 19:33:30

by Paul Moore

[permalink] [raw]

Subject: Re: [PATCH] audit, io_uring, io-wq: Fix memory leak in io_sq_thread() and io_wqe_worker()

On Wed, Aug 3, 2022 at 9:16 AM Paul Moore <[email protected]> wrote:
> On Wed, Aug 3, 2022 at 1:03 AM Peilin Ye <[email protected]> wrote:
> >
> > Currently @audit_context is allocated twice for io_uring workers:
> >
> > 1. copy_process() calls audit_alloc();
> > 2. io_sq_thread() or io_wqe_worker() calls audit_alloc_kernel() (which
> > is effectively audit_alloc()) and overwrites @audit_context,
> > causing:
> >
> > BUG: memory leak
> > unreferenced object 0xffff888144547400 (size 1024):
> > <...>
> > hex dump (first 32 bytes):
> > 00 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00 ................
> > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> > backtrace:
> > [<ffffffff8135cfc3>] audit_alloc+0x133/0x210
> > [<ffffffff81239e63>] copy_process+0xcd3/0x2340
> > [<ffffffff8123b5f3>] create_io_thread+0x63/0x90
> > [<ffffffff81686604>] create_io_worker+0xb4/0x230
> > [<ffffffff81686f68>] io_wqe_enqueue+0x248/0x3b0
> > [<ffffffff8167663a>] io_queue_iowq+0xba/0x200
> > [<ffffffff816768b3>] io_queue_async+0x113/0x180
> > [<ffffffff816840df>] io_req_task_submit+0x18f/0x1a0
> > [<ffffffff816841cd>] io_apoll_task_func+0xdd/0x120
> > [<ffffffff8167d49f>] tctx_task_work+0x11f/0x570
> > [<ffffffff81272c4e>] task_work_run+0x7e/0xc0
> > [<ffffffff8125a688>] get_signal+0xc18/0xf10
> > [<ffffffff8111645b>] arch_do_signal_or_restart+0x2b/0x730
> > [<ffffffff812ea44e>] exit_to_user_mode_prepare+0x5e/0x180
> > [<ffffffff844ae1b2>] syscall_exit_to_user_mode+0x12/0x20
> > [<ffffffff844a7e80>] do_syscall_64+0x40/0x80
> >
> > Then,
> >
> > 3. io_sq_thread() or io_wqe_worker() frees @audit_context using
> > audit_free();
> > 4. do_exit() eventually calls audit_free() again, which is okay
> > because audit_free() does a NULL check.
> >
> > Free the old @audit_context first in audit_alloc_kernel(), and delete
> > the redundant calls to audit_free() for less confusion.
> >
> > Fixes: 5bd2182d58e9 ("audit,io_uring,io-wq: add some basic audit support to io_uring")
> > Cc: [email protected]
> > Signed-off-by: Peilin Ye <[email protected]>
> > ---
> > Hi all,
> >
> > A better way to fix this memleak would probably be checking
> > @args->io_thread in copy_process()? Something like:
> >
> > if (args->io_thread)
> > retval = audit_alloc_kernel();
> > else
> > retval = audit_alloc();
> >
> > But I didn't want to add another if to copy_process() for this bugfix.
> > Please suggest, thanks!
>
> Thanks for the report and patch! I'll take a closer look at this
> today and get back to you.

I think the best solution to this is simply to remove the calls to
audit_alloc_kernel() in the io_uring and io-wq code, as well as the
audit_alloc_kernel() function itself. As long as create_io_thread()
ends up calling copy_process to create the new kernel thread the
audit_context should be allocated correctly. Peilin Ye, are you able
to draft a patch to do that and give it a test?

For those that may be wondering how this happened (I definitely was!),
it looks like when I first started working on the LSM/audit support
for io_uring it was before the v5.12-rc1 release when
create_io_thread() was introduced. Prior to create_io_thread() it
appears that io_uring/io-wq wasn't calling into copy_process() and
thus was not getting an audit_context allocated in the kernel thread's
task_struct; the solution for those original development drafts was to
add a call to a new audit_alloc_kernel() which would handle the
audit_context allocation. Unfortunately, I didn't notice the move to
create_io_thread() during development and the redundant
audit_alloc_kernel() calls remained :/

--
paul-moore.com

2022-08-03 20:26:29

by Peilin Ye

[permalink] [raw]

Subject: Re: [PATCH] audit, io_uring, io-wq: Fix memory leak in io_sq_thread() and io_wqe_worker()

Hi,

On Wed, Aug 03, 2022 at 03:28:19PM -0400, Paul Moore wrote:
> On Wed, Aug 3, 2022 at 9:16 AM Paul Moore <[email protected]> wrote:
> > On Wed, Aug 3, 2022 at 1:03 AM Peilin Ye <[email protected]> wrote:
> > > Hi all,
> > >
> > > A better way to fix this memleak would probably be checking
> > > @args->io_thread in copy_process()? Something like:
> > >
> > > if (args->io_thread)
> > > retval = audit_alloc_kernel();
> > > else
> > > retval = audit_alloc();
> > >
> > > But I didn't want to add another if to copy_process() for this bugfix.
> > > Please suggest, thanks!
> >
> > Thanks for the report and patch! I'll take a closer look at this
> > today and get back to you.
>
> I think the best solution to this is simply to remove the calls to
> audit_alloc_kernel() in the io_uring and io-wq code, as well as the
> audit_alloc_kernel() function itself. As long as create_io_thread()
> ends up calling copy_process to create the new kernel thread the
> audit_context should be allocated correctly. Peilin Ye, are you able
> to draft a patch to do that and give it a test?

Sure, I will write a v2 today. Thanks for the suggestion!

> For those that may be wondering how this happened (I definitely was!),
> it looks like when I first started working on the LSM/audit support
> for io_uring it was before the v5.12-rc1 release when
> create_io_thread() was introduced. Prior to create_io_thread() it
> appears that io_uring/io-wq wasn't calling into copy_process() and
> thus was not getting an audit_context allocated in the kernel thread's
> task_struct; the solution for those original development drafts was to
> add a call to a new audit_alloc_kernel() which would handle the
> audit_context allocation. Unfortunately, I didn't notice the move to
> create_io_thread() during development and the redundant
> audit_alloc_kernel() calls remained :/

Thanks,
Peilin Ye

2022-08-03 21:20:47

by Jens Axboe

[permalink] [raw]

Subject: Re: [PATCH] audit, io_uring, io-wq: Fix memory leak in io_sq_thread() and io_wqe_worker()

On 8/3/22 1:28 PM, Paul Moore wrote:
> On Wed, Aug 3, 2022 at 9:16 AM Paul Moore <[email protected]> wrote:
>> On Wed, Aug 3, 2022 at 1:03 AM Peilin Ye <[email protected]> wrote:
>>>
>>> Currently @audit_context is allocated twice for io_uring workers:
>>>
>>> 1. copy_process() calls audit_alloc();
>>> 2. io_sq_thread() or io_wqe_worker() calls audit_alloc_kernel() (which
>>> is effectively audit_alloc()) and overwrites @audit_context,
>>> causing:
>>>
>>> BUG: memory leak
>>> unreferenced object 0xffff888144547400 (size 1024):
>>> <...>
>>> hex dump (first 32 bytes):
>>> 00 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00 ................
>>> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
>>> backtrace:
>>> [<ffffffff8135cfc3>] audit_alloc+0x133/0x210
>>> [<ffffffff81239e63>] copy_process+0xcd3/0x2340
>>> [<ffffffff8123b5f3>] create_io_thread+0x63/0x90
>>> [<ffffffff81686604>] create_io_worker+0xb4/0x230
>>> [<ffffffff81686f68>] io_wqe_enqueue+0x248/0x3b0
>>> [<ffffffff8167663a>] io_queue_iowq+0xba/0x200
>>> [<ffffffff816768b3>] io_queue_async+0x113/0x180
>>> [<ffffffff816840df>] io_req_task_submit+0x18f/0x1a0
>>> [<ffffffff816841cd>] io_apoll_task_func+0xdd/0x120
>>> [<ffffffff8167d49f>] tctx_task_work+0x11f/0x570
>>> [<ffffffff81272c4e>] task_work_run+0x7e/0xc0
>>> [<ffffffff8125a688>] get_signal+0xc18/0xf10
>>> [<ffffffff8111645b>] arch_do_signal_or_restart+0x2b/0x730
>>> [<ffffffff812ea44e>] exit_to_user_mode_prepare+0x5e/0x180
>>> [<ffffffff844ae1b2>] syscall_exit_to_user_mode+0x12/0x20
>>> [<ffffffff844a7e80>] do_syscall_64+0x40/0x80
>>>
>>> Then,
>>>
>>> 3. io_sq_thread() or io_wqe_worker() frees @audit_context using
>>> audit_free();
>>> 4. do_exit() eventually calls audit_free() again, which is okay
>>> because audit_free() does a NULL check.
>>>
>>> Free the old @audit_context first in audit_alloc_kernel(), and delete
>>> the redundant calls to audit_free() for less confusion.
>>>
>>> Fixes: 5bd2182d58e9 ("audit,io_uring,io-wq: add some basic audit support to io_uring")
>>> Cc: [email protected]
>>> Signed-off-by: Peilin Ye <[email protected]>
>>> ---
>>> Hi all,
>>>
>>> A better way to fix this memleak would probably be checking
>>> @args->io_thread in copy_process()? Something like:
>>>
>>> if (args->io_thread)
>>> retval = audit_alloc_kernel();
>>> else
>>> retval = audit_alloc();
>>>
>>> But I didn't want to add another if to copy_process() for this bugfix.
>>> Please suggest, thanks!
>>
>> Thanks for the report and patch! I'll take a closer look at this
>> today and get back to you.
>
> I think the best solution to this is simply to remove the calls to
> audit_alloc_kernel() in the io_uring and io-wq code, as well as the
> audit_alloc_kernel() function itself. As long as create_io_thread()
> ends up calling copy_process to create the new kernel thread the
> audit_context should be allocated correctly. Peilin Ye, are you able
> to draft a patch to do that and give it a test?
>
> For those that may be wondering how this happened (I definitely was!),
> it looks like when I first started working on the LSM/audit support
> for io_uring it was before the v5.12-rc1 release when
> create_io_thread() was introduced. Prior to create_io_thread() it
> appears that io_uring/io-wq wasn't calling into copy_process() and
> thus was not getting an audit_context allocated in the kernel thread's
> task_struct; the solution for those original development drafts was to
> add a call to a new audit_alloc_kernel() which would handle the
> audit_context allocation. Unfortunately, I didn't notice the move to
> create_io_thread() during development and the redundant
> audit_alloc_kernel() calls remained :/

I agree with your analysis and suggested solution. Post the native io-wq
workers create_io_thread() -> copy_process() is always used for io-wq
(and sqpoll, for that matter).

--
Jens Axboe

2022-08-03 22:31:30

by Peilin Ye

[permalink] [raw]

Subject: [PATCH v2] audit, io_uring, io-wq: Fix memory leak in io_sq_thread() and io_wqe_worker()

From: Peilin Ye <[email protected]>

Currently @audit_context is allocated twice for io_uring workers:

1. copy_process() calls audit_alloc();
2. io_sq_thread() or io_wqe_worker() calls audit_alloc_kernel() (which
is effectively audit_alloc()) and overwrites @audit_context,
causing:

BUG: memory leak
unreferenced object 0xffff888144547400 (size 1024):
<...>
hex dump (first 32 bytes):
00 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00 ................
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
backtrace:
[<ffffffff8135cfc3>] audit_alloc+0x133/0x210
[<ffffffff81239e63>] copy_process+0xcd3/0x2340
[<ffffffff8123b5f3>] create_io_thread+0x63/0x90
[<ffffffff81686604>] create_io_worker+0xb4/0x230
[<ffffffff81686f68>] io_wqe_enqueue+0x248/0x3b0
[<ffffffff8167663a>] io_queue_iowq+0xba/0x200
[<ffffffff816768b3>] io_queue_async+0x113/0x180
[<ffffffff816840df>] io_req_task_submit+0x18f/0x1a0
[<ffffffff816841cd>] io_apoll_task_func+0xdd/0x120
[<ffffffff8167d49f>] tctx_task_work+0x11f/0x570
[<ffffffff81272c4e>] task_work_run+0x7e/0xc0
[<ffffffff8125a688>] get_signal+0xc18/0xf10
[<ffffffff8111645b>] arch_do_signal_or_restart+0x2b/0x730
[<ffffffff812ea44e>] exit_to_user_mode_prepare+0x5e/0x180
[<ffffffff844ae1b2>] syscall_exit_to_user_mode+0x12/0x20
[<ffffffff844a7e80>] do_syscall_64+0x40/0x80

Then,

3. io_sq_thread() or io_wqe_worker() frees @audit_context using
audit_free();
4. do_exit() eventually calls audit_free() again, which is okay
because audit_free() does a NULL check.

As suggested by Paul Moore, fix it by deleting audit_alloc_kernel() and
redundant audit_free() calls.

Fixes: 5bd2182d58e9 ("audit,io_uring,io-wq: add some basic audit support to io_uring")
Suggested-by: Paul Moore <[email protected]>
Cc: [email protected]
Signed-off-by: Peilin Ye <[email protected]>
---
Change since v1:
- Delete audit_alloc_kernel() (Paul Moore)

fs/io-wq.c | 3 ---
fs/io_uring.c | 4 ----
include/linux/audit.h | 5 -----
kernel/auditsc.c | 25 -------------------------
4 files changed, 37 deletions(-)

diff --git a/fs/io-wq.c b/fs/io-wq.c
index 824623bcf1a5..4d8a77a2a150 100644
--- a/fs/io-wq.c
+++ b/fs/io-wq.c
@@ -634,8 +634,6 @@ static int io_wqe_worker(void *data)
snprintf(buf, sizeof(buf), "iou-wrk-%d", wq->task->pid);
set_task_comm(current, buf);

- audit_alloc_kernel(current);
-
while (!test_bit(IO_WQ_BIT_EXIT, &wq->state)) {
long ret;

@@ -670,7 +668,6 @@ static int io_wqe_worker(void *data)
if (test_bit(IO_WQ_BIT_EXIT, &wq->state))
io_worker_handle_work(worker);

- audit_free(current);
io_worker_exit(worker);
return 0;
}
diff --git a/fs/io_uring.c b/fs/io_uring.c
index e8e769be9ed0..e0da0d2f71f2 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -9208,8 +9208,6 @@ static int io_sq_thread(void *data)
set_cpus_allowed_ptr(current, cpu_online_mask);
current->flags |= PF_NO_SETAFFINITY;

- audit_alloc_kernel(current);
-
mutex_lock(&sqd->lock);
while (1) {
bool cap_entries, sqt_spin = false;
@@ -9283,8 +9281,6 @@ static int io_sq_thread(void *data)
io_run_task_work();
mutex_unlock(&sqd->lock);

- audit_free(current);
-
complete(&sqd->exited);
do_exit(0);
}
diff --git a/include/linux/audit.h b/include/linux/audit.h
index cece70231138..c313df466e6e 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -287,7 +287,6 @@ static inline int audit_signal_info(int sig, struct task_struct *t)
/* These are defined in auditsc.c */
/* Public API */
extern int audit_alloc(struct task_struct *task);
-extern int audit_alloc_kernel(struct task_struct *task);
extern void __audit_free(struct task_struct *task);
extern void __audit_uring_entry(u8 op);
extern void __audit_uring_exit(int success, long code);
@@ -580,10 +579,6 @@ static inline int audit_alloc(struct task_struct *task)
{
return 0;
}
-static inline int audit_alloc_kernel(struct task_struct *task)
-{
- return 0;
-}
static inline void audit_free(struct task_struct *task)
{ }
static inline void audit_uring_entry(u8 op)
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 3a8c9d744800..dd8d9ab747c3 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -1073,31 +1073,6 @@ int audit_alloc(struct task_struct *tsk)
return 0;
}

-/**
- * audit_alloc_kernel - allocate an audit_context for a kernel task
- * @tsk: the kernel task
- *
- * Similar to the audit_alloc() function, but intended for kernel private
- * threads. Returns zero on success, negative values on failure.
- */
-int audit_alloc_kernel(struct task_struct *tsk)
-{
- /*
- * At the moment we are just going to call into audit_alloc() to
- * simplify the code, but there two things to keep in mind with this
- * approach:
- *
- * 1. Filtering internal kernel tasks is a bit laughable in almost all
- * cases, but there is at least one case where there is a benefit:
- * the '-a task,never' case allows the admin to effectively disable
- * task auditing at runtime.
- *
- * 2. The {set,clear}_task_syscall_work() ops likely have zero effect
- * on these internal kernel tasks, but they probably don't hurt either.
- */
- return audit_alloc(tsk);
-}
-
static inline void audit_free_context(struct audit_context *context)
{
/* resetting is extra work, but it is likely just noise */
--
2.20.1

2022-08-04 14:11:02

by Paul Moore

[permalink] [raw]

Subject: Re: [PATCH v2] audit, io_uring, io-wq: Fix memory leak in io_sq_thread() and io_wqe_worker()

On Wed, Aug 3, 2022 at 6:24 PM Peilin Ye <[email protected]> wrote:
>
> From: Peilin Ye <[email protected]>
>
> Currently @audit_context is allocated twice for io_uring workers:
>
> 1. copy_process() calls audit_alloc();
> 2. io_sq_thread() or io_wqe_worker() calls audit_alloc_kernel() (which
> is effectively audit_alloc()) and overwrites @audit_context,
> causing:
>
> BUG: memory leak
> unreferenced object 0xffff888144547400 (size 1024):
> <...>
> hex dump (first 32 bytes):
> 00 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00 ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> backtrace:
> [<ffffffff8135cfc3>] audit_alloc+0x133/0x210
> [<ffffffff81239e63>] copy_process+0xcd3/0x2340
> [<ffffffff8123b5f3>] create_io_thread+0x63/0x90
> [<ffffffff81686604>] create_io_worker+0xb4/0x230
> [<ffffffff81686f68>] io_wqe_enqueue+0x248/0x3b0
> [<ffffffff8167663a>] io_queue_iowq+0xba/0x200
> [<ffffffff816768b3>] io_queue_async+0x113/0x180
> [<ffffffff816840df>] io_req_task_submit+0x18f/0x1a0
> [<ffffffff816841cd>] io_apoll_task_func+0xdd/0x120
> [<ffffffff8167d49f>] tctx_task_work+0x11f/0x570
> [<ffffffff81272c4e>] task_work_run+0x7e/0xc0
> [<ffffffff8125a688>] get_signal+0xc18/0xf10
> [<ffffffff8111645b>] arch_do_signal_or_restart+0x2b/0x730
> [<ffffffff812ea44e>] exit_to_user_mode_prepare+0x5e/0x180
> [<ffffffff844ae1b2>] syscall_exit_to_user_mode+0x12/0x20
> [<ffffffff844a7e80>] do_syscall_64+0x40/0x80
>
> Then,
>
> 3. io_sq_thread() or io_wqe_worker() frees @audit_context using
> audit_free();
> 4. do_exit() eventually calls audit_free() again, which is okay
> because audit_free() does a NULL check.
>
> As suggested by Paul Moore, fix it by deleting audit_alloc_kernel() and
> redundant audit_free() calls.
>
> Fixes: 5bd2182d58e9 ("audit,io_uring,io-wq: add some basic audit support to io_uring")
> Suggested-by: Paul Moore <[email protected]>
> Cc: [email protected]
> Signed-off-by: Peilin Ye <[email protected]>
> ---
> Change since v1:
> - Delete audit_alloc_kernel() (Paul Moore)
>
> fs/io-wq.c | 3 ---
> fs/io_uring.c | 4 ----
> include/linux/audit.h | 5 -----
> kernel/auditsc.c | 25 -------------------------
> 4 files changed, 37 deletions(-)

This looks good to me, thanks! Although it looks like the io_uring
related changes will need to be applied by hand as they are pointing
to the old layout under fs/ as opposed to the newer layout in
io_uring/ introduced during this merge window.

Jens, did you want to take this via the io_uring tree or should I take
it via the audit tree? If the latter, an ACK would be appreciated, if
the former my ACK is below.

Acked-by: Paul Moore <[email protected]>

--
paul-moore.com

2022-08-04 14:37:58

by Jens Axboe

[permalink] [raw]

Subject: Re: [PATCH v2] audit, io_uring, io-wq: Fix memory leak in io_sq_thread() and io_wqe_worker()

On 8/4/22 7:51 AM, Paul Moore wrote:
> On Wed, Aug 3, 2022 at 6:24 PM Peilin Ye <[email protected]> wrote:
>>
>> From: Peilin Ye <[email protected]>
>>
>> Currently @audit_context is allocated twice for io_uring workers:
>>
>> 1. copy_process() calls audit_alloc();
>> 2. io_sq_thread() or io_wqe_worker() calls audit_alloc_kernel() (which
>> is effectively audit_alloc()) and overwrites @audit_context,
>> causing:
>>
>> BUG: memory leak
>> unreferenced object 0xffff888144547400 (size 1024):
>> <...>
>> hex dump (first 32 bytes):
>> 00 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00 ................
>> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
>> backtrace:
>> [<ffffffff8135cfc3>] audit_alloc+0x133/0x210
>> [<ffffffff81239e63>] copy_process+0xcd3/0x2340
>> [<ffffffff8123b5f3>] create_io_thread+0x63/0x90
>> [<ffffffff81686604>] create_io_worker+0xb4/0x230
>> [<ffffffff81686f68>] io_wqe_enqueue+0x248/0x3b0
>> [<ffffffff8167663a>] io_queue_iowq+0xba/0x200
>> [<ffffffff816768b3>] io_queue_async+0x113/0x180
>> [<ffffffff816840df>] io_req_task_submit+0x18f/0x1a0
>> [<ffffffff816841cd>] io_apoll_task_func+0xdd/0x120
>> [<ffffffff8167d49f>] tctx_task_work+0x11f/0x570
>> [<ffffffff81272c4e>] task_work_run+0x7e/0xc0
>> [<ffffffff8125a688>] get_signal+0xc18/0xf10
>> [<ffffffff8111645b>] arch_do_signal_or_restart+0x2b/0x730
>> [<ffffffff812ea44e>] exit_to_user_mode_prepare+0x5e/0x180
>> [<ffffffff844ae1b2>] syscall_exit_to_user_mode+0x12/0x20
>> [<ffffffff844a7e80>] do_syscall_64+0x40/0x80
>>
>> Then,
>>
>> 3. io_sq_thread() or io_wqe_worker() frees @audit_context using
>> audit_free();
>> 4. do_exit() eventually calls audit_free() again, which is okay
>> because audit_free() does a NULL check.
>>
>> As suggested by Paul Moore, fix it by deleting audit_alloc_kernel() and
>> redundant audit_free() calls.
>>
>> Fixes: 5bd2182d58e9 ("audit,io_uring,io-wq: add some basic audit support to io_uring")
>> Suggested-by: Paul Moore <[email protected]>
>> Cc: [email protected]
>> Signed-off-by: Peilin Ye <[email protected]>
>> ---
>> Change since v1:
>> - Delete audit_alloc_kernel() (Paul Moore)
>>
>> fs/io-wq.c | 3 ---
>> fs/io_uring.c | 4 ----
>> include/linux/audit.h | 5 -----
>> kernel/auditsc.c | 25 -------------------------
>> 4 files changed, 37 deletions(-)
>
> This looks good to me, thanks! Although it looks like the io_uring
> related changes will need to be applied by hand as they are pointing
> to the old layout under fs/ as opposed to the newer layout in
> io_uring/ introduced during this merge window.
>
> Jens, did you want to take this via the io_uring tree or should I take
> it via the audit tree? If the latter, an ACK would be appreciated, if
> the former my ACK is below.
>
> Acked-by: Paul Moore <[email protected]>

Probably better if I take it, since I need to massage it into the
current tree anyway. We can then use this one as the base for the stable
backports that are going to be required.

--
Jens Axboe

2022-08-04 14:38:30

by Jens Axboe

[permalink] [raw]

Subject: Re: [PATCH v2] audit, io_uring, io-wq: Fix memory leak in io_sq_thread() and io_wqe_worker()

On Wed, 3 Aug 2022 15:23:43 -0700, Peilin Ye wrote:
> From: Peilin Ye <[email protected]>
>
> Currently @audit_context is allocated twice for io_uring workers:
>
> 1. copy_process() calls audit_alloc();
> 2. io_sq_thread() or io_wqe_worker() calls audit_alloc_kernel() (which
> is effectively audit_alloc()) and overwrites @audit_context,
> causing:
>
> [...]

Applied, thanks!

[1/1] audit, io_uring, io-wq: Fix memory leak in io_sq_thread() and io_wqe_worker()
commit: f482aa98652795846cc55da98ebe331eb74f3d0b

Best regards,
--
Jens Axboe

2022-08-04 15:57:57

by Paul Moore

[permalink] [raw]

Subject: Re: [PATCH v2] audit, io_uring, io-wq: Fix memory leak in io_sq_thread() and io_wqe_worker()

On Thu, Aug 4, 2022 at 10:32 AM Jens Axboe <[email protected]> wrote:
> On 8/4/22 7:51 AM, Paul Moore wrote:
> > On Wed, Aug 3, 2022 at 6:24 PM Peilin Ye <[email protected]> wrote:
> >>
> >> From: Peilin Ye <[email protected]>
> >>
> >> Currently @audit_context is allocated twice for io_uring workers:
> >>
> >> 1. copy_process() calls audit_alloc();
> >> 2. io_sq_thread() or io_wqe_worker() calls audit_alloc_kernel() (which
> >> is effectively audit_alloc()) and overwrites @audit_context,
> >> causing:
> >>
> >> BUG: memory leak
> >> unreferenced object 0xffff888144547400 (size 1024):
> >> <...>
> >> hex dump (first 32 bytes):
> >> 00 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00 ................
> >> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> >> backtrace:
> >> [<ffffffff8135cfc3>] audit_alloc+0x133/0x210
> >> [<ffffffff81239e63>] copy_process+0xcd3/0x2340
> >> [<ffffffff8123b5f3>] create_io_thread+0x63/0x90
> >> [<ffffffff81686604>] create_io_worker+0xb4/0x230
> >> [<ffffffff81686f68>] io_wqe_enqueue+0x248/0x3b0
> >> [<ffffffff8167663a>] io_queue_iowq+0xba/0x200
> >> [<ffffffff816768b3>] io_queue_async+0x113/0x180
> >> [<ffffffff816840df>] io_req_task_submit+0x18f/0x1a0
> >> [<ffffffff816841cd>] io_apoll_task_func+0xdd/0x120
> >> [<ffffffff8167d49f>] tctx_task_work+0x11f/0x570
> >> [<ffffffff81272c4e>] task_work_run+0x7e/0xc0
> >> [<ffffffff8125a688>] get_signal+0xc18/0xf10
> >> [<ffffffff8111645b>] arch_do_signal_or_restart+0x2b/0x730
> >> [<ffffffff812ea44e>] exit_to_user_mode_prepare+0x5e/0x180
> >> [<ffffffff844ae1b2>] syscall_exit_to_user_mode+0x12/0x20
> >> [<ffffffff844a7e80>] do_syscall_64+0x40/0x80
> >>
> >> Then,
> >>
> >> 3. io_sq_thread() or io_wqe_worker() frees @audit_context using
> >> audit_free();
> >> 4. do_exit() eventually calls audit_free() again, which is okay
> >> because audit_free() does a NULL check.
> >>
> >> As suggested by Paul Moore, fix it by deleting audit_alloc_kernel() and
> >> redundant audit_free() calls.
> >>
> >> Fixes: 5bd2182d58e9 ("audit,io_uring,io-wq: add some basic audit support to io_uring")
> >> Suggested-by: Paul Moore <[email protected]>
> >> Cc: [email protected]
> >> Signed-off-by: Peilin Ye <[email protected]>
> >> ---
> >> Change since v1:
> >> - Delete audit_alloc_kernel() (Paul Moore)
> >>
> >> fs/io-wq.c | 3 ---
> >> fs/io_uring.c | 4 ----
> >> include/linux/audit.h | 5 -----
> >> kernel/auditsc.c | 25 -------------------------
> >> 4 files changed, 37 deletions(-)
> >
> > This looks good to me, thanks! Although it looks like the io_uring
> > related changes will need to be applied by hand as they are pointing
> > to the old layout under fs/ as opposed to the newer layout in
> > io_uring/ introduced during this merge window.
> >
> > Jens, did you want to take this via the io_uring tree or should I take
> > it via the audit tree? If the latter, an ACK would be appreciated, if
> > the former my ACK is below.
> >
> > Acked-by: Paul Moore <[email protected]>
>
> Probably better if I take it, since I need to massage it into the
> current tree anyway. We can then use this one as the base for the stable
> backports that are going to be required.

Sounds good to me, thanks everyone.

--
paul-moore.com