* [PATCH] mm/gup: fix null pointer dereference detected by coverity
@ 2020-04-07 9:51 Miles Chen
2020-04-07 18:19 ` Ira Weiny
2020-04-15 0:08 ` Andrew Morton
0 siblings, 2 replies; 5+ messages in thread
From: Miles Chen @ 2020-04-07 9:51 UTC (permalink / raw)
To: Andrew Morton
Cc: linux-mm, linux-kernel, linux-mediatek, wsd_upstream, Miles Chen
In fixup_user_fault(), it is possible that unlocked is NULL,
so we should test unlocked before using it.
For example, in arch/arc/kernel/process.c, NULL is passed
to fixup_user_fault().
SYSCALL_DEFINE3(arc_usr_cmpxchg, int *, uaddr, int, expected, int, new)
{
...
ret = fixup_user_fault(current, current->mm, (unsigned long) uaddr,
FAULT_FLAG_WRITE, NULL);
...
}
Fixes: 4a9e1cda2748 ("mm: bring in additional flag for fixup_user_fault to signal unlock")
Signed-off-by: Miles Chen <miles.chen@mediatek.com>
---
mm/gup.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/mm/gup.c b/mm/gup.c
index da3e03185144..a68d11dc232d 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1230,7 +1230,8 @@ int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
if (ret & VM_FAULT_RETRY) {
down_read(&mm->mmap_sem);
if (!(fault_flags & FAULT_FLAG_TRIED)) {
- *unlocked = true;
+ if (unlocked)
+ *unlocked = true;
fault_flags |= FAULT_FLAG_TRIED;
goto retry;
}
--
2.18.0
^ permalink raw reply related [flat|nested] 5+ messages in thread* Re: [PATCH] mm/gup: fix null pointer dereference detected by coverity
2020-04-07 9:51 [PATCH] mm/gup: fix null pointer dereference detected by coverity Miles Chen
@ 2020-04-07 18:19 ` Ira Weiny
2020-04-14 19:55 ` Souptick Joarder
2020-04-15 0:08 ` Andrew Morton
1 sibling, 1 reply; 5+ messages in thread
From: Ira Weiny @ 2020-04-07 18:19 UTC (permalink / raw)
To: Miles Chen
Cc: Andrew Morton, linux-mm, linux-kernel, linux-mediatek, wsd_upstream
On Tue, Apr 07, 2020 at 05:51:07PM +0800, Miles Chen wrote:
> In fixup_user_fault(), it is possible that unlocked is NULL,
> so we should test unlocked before using it.
>
> For example, in arch/arc/kernel/process.c, NULL is passed
> to fixup_user_fault().
>
> SYSCALL_DEFINE3(arc_usr_cmpxchg, int *, uaddr, int, expected, int, new)
> {
> ...
> ret = fixup_user_fault(current, current->mm, (unsigned long) uaddr,
> FAULT_FLAG_WRITE, NULL);
> ...
> }
>
> Fixes: 4a9e1cda2748 ("mm: bring in additional flag for fixup_user_fault to signal unlock")
> Signed-off-by: Miles Chen <miles.chen@mediatek.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
> ---
> mm/gup.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/mm/gup.c b/mm/gup.c
> index da3e03185144..a68d11dc232d 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -1230,7 +1230,8 @@ int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
> if (ret & VM_FAULT_RETRY) {
> down_read(&mm->mmap_sem);
> if (!(fault_flags & FAULT_FLAG_TRIED)) {
> - *unlocked = true;
> + if (unlocked)
> + *unlocked = true;
> fault_flags |= FAULT_FLAG_TRIED;
> goto retry;
> }
> --
> 2.18.0
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH] mm/gup: fix null pointer dereference detected by coverity
2020-04-07 18:19 ` Ira Weiny
@ 2020-04-14 19:55 ` Souptick Joarder
0 siblings, 0 replies; 5+ messages in thread
From: Souptick Joarder @ 2020-04-14 19:55 UTC (permalink / raw)
To: Ira Weiny
Cc: Miles Chen, Andrew Morton, Linux-MM, linux-kernel,
linux-mediatek, wsd_upstream
On Tue, Apr 7, 2020 at 11:49 PM Ira Weiny <ira.weiny@intel.com> wrote:
>
> On Tue, Apr 07, 2020 at 05:51:07PM +0800, Miles Chen wrote:
> > In fixup_user_fault(), it is possible that unlocked is NULL,
> > so we should test unlocked before using it.
> >
> > For example, in arch/arc/kernel/process.c, NULL is passed
> > to fixup_user_fault().
> >
> > SYSCALL_DEFINE3(arc_usr_cmpxchg, int *, uaddr, int, expected, int, new)
> > {
> > ...
> > ret = fixup_user_fault(current, current->mm, (unsigned long) uaddr,
> > FAULT_FLAG_WRITE, NULL);
> > ...
> > }
> >
> > Fixes: 4a9e1cda2748 ("mm: bring in additional flag for fixup_user_fault to signal unlock")
> > Signed-off-by: Miles Chen <miles.chen@mediatek.com>
>
> Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Acked-by: Souptick Joarder <jrdr.linux@gmail.com>
>
> > ---
> > mm/gup.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/mm/gup.c b/mm/gup.c
> > index da3e03185144..a68d11dc232d 100644
> > --- a/mm/gup.c
> > +++ b/mm/gup.c
> > @@ -1230,7 +1230,8 @@ int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
> > if (ret & VM_FAULT_RETRY) {
> > down_read(&mm->mmap_sem);
> > if (!(fault_flags & FAULT_FLAG_TRIED)) {
> > - *unlocked = true;
> > + if (unlocked)
> > + *unlocked = true;
> > fault_flags |= FAULT_FLAG_TRIED;
> > goto retry;
> > }
> > --
> > 2.18.0
>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] mm/gup: fix null pointer dereference detected by coverity
2020-04-07 9:51 [PATCH] mm/gup: fix null pointer dereference detected by coverity Miles Chen
2020-04-07 18:19 ` Ira Weiny
@ 2020-04-15 0:08 ` Andrew Morton
2020-04-15 1:53 ` Miles Chen
1 sibling, 1 reply; 5+ messages in thread
From: Andrew Morton @ 2020-04-15 0:08 UTC (permalink / raw)
To: Miles Chen; +Cc: linux-mm, linux-kernel, linux-mediatek, wsd_upstream, Peter Xu
On Tue, 7 Apr 2020 17:51:07 +0800 Miles Chen <miles.chen@mediatek.com> wrote:
> In fixup_user_fault(), it is possible that unlocked is NULL,
> so we should test unlocked before using it.
>
> For example, in arch/arc/kernel/process.c, NULL is passed
> to fixup_user_fault().
>
> SYSCALL_DEFINE3(arc_usr_cmpxchg, int *, uaddr, int, expected, int, new)
> {
> ...
> ret = fixup_user_fault(current, current->mm, (unsigned long) uaddr,
> FAULT_FLAG_WRITE, NULL);
> ...
> }
(cc Peter)
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -1230,7 +1230,8 @@ int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
> if (ret & VM_FAULT_RETRY) {
> down_read(&mm->mmap_sem);
> if (!(fault_flags & FAULT_FLAG_TRIED)) {
> - *unlocked = true;
> + if (unlocked)
> + *unlocked = true;
> fault_flags |= FAULT_FLAG_TRIED;
> goto retry;
> }
Not sure. If the caller passes FAULT_FLAG_ALLOW_RETRY then they must
also pass in a valid non-NULL `unlocked'. If the caller passed
FAULT_FLAG_ALLOW_RETRY and unlocked==NULL then the resulting oops is an
appropriate way of reporting this mistake. I think?
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH] mm/gup: fix null pointer dereference detected by coverity
2020-04-15 0:08 ` Andrew Morton
@ 2020-04-15 1:53 ` Miles Chen
0 siblings, 0 replies; 5+ messages in thread
From: Miles Chen @ 2020-04-15 1:53 UTC (permalink / raw)
To: Andrew Morton
Cc: linux-mm, linux-kernel, linux-mediatek, wsd_upstream, Peter Xu
On Tue, 2020-04-14 at 17:08 -0700, Andrew Morton wrote:
> On Tue, 7 Apr 2020 17:51:07 +0800 Miles Chen <miles.chen@mediatek.com> wrote:
>
> > In fixup_user_fault(), it is possible that unlocked is NULL,
> > so we should test unlocked before using it.
> >
> > For example, in arch/arc/kernel/process.c, NULL is passed
> > to fixup_user_fault().
> >
> > SYSCALL_DEFINE3(arc_usr_cmpxchg, int *, uaddr, int, expected, int, new)
> > {
> > ...
> > ret = fixup_user_fault(current, current->mm, (unsigned long) uaddr,
> > FAULT_FLAG_WRITE, NULL);
> > ...
> > }
>
> (cc Peter)
>
> > --- a/mm/gup.c
> > +++ b/mm/gup.c
> > @@ -1230,7 +1230,8 @@ int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
> > if (ret & VM_FAULT_RETRY) {
> > down_read(&mm->mmap_sem);
> > if (!(fault_flags & FAULT_FLAG_TRIED)) {
> > - *unlocked = true;
> > + if (unlocked)
> > + *unlocked = true;
> > fault_flags |= FAULT_FLAG_TRIED;
> > goto retry;
> > }
>
> Not sure. If the caller passes FAULT_FLAG_ALLOW_RETRY then they must
> also pass in a valid non-NULL `unlocked'. If the caller passed
> FAULT_FLAG_ALLOW_RETRY and unlocked==NULL then the resulting oops is an
> appropriate way of reporting this mistake. I think?
>
Agree. How about put "unlocked==NULL must not be used with
FAULT_FLAG_ALLOW_RETRY." in the comment? Make it easier to understand
the oops.
e.g.,
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1176,7 +1176,8 @@ static bool vma_permits_fault(struct
vm_area_struct *vma,
* @address: user address
* @fault_flags:flags to pass down to handle_mm_fault()
* @unlocked: did we unlock the mmap_sem while retrying, maybe NULL if
caller
- * does not allow retry
+ * does not allow retry. If NULL, the caller must guarantee
+ * the fault_flags does not contain FAULT_FLAG_ALLOW_RETRY.
^ permalink raw reply [flat|nested] 5+ messages in thread
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2020-04-07 9:51 [PATCH] mm/gup: fix null pointer dereference detected by coverity Miles Chen
2020-04-07 18:19 ` Ira Weiny
2020-04-14 19:55 ` Souptick Joarder
2020-04-15 0:08 ` Andrew Morton
2020-04-15 1:53 ` Miles Chen
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