* [PATCH v2] Fixes: null pointer dereference in pfnmap_lockdep_assert
@ 2024-10-04 13:05 Manas via B4 Relay
2024-10-04 13:21 ` Peter Xu
0 siblings, 1 reply; 3+ messages in thread
From: Manas via B4 Relay @ 2024-10-04 13:05 UTC (permalink / raw)
To: Andrew Morton
Cc: Peter Xu, Shuah Khan, Anup Sharma, linux-mm, linux-kernel,
syzbot+093d096417e7038a689b, Manas
From: Manas <manas18244@iiitd.ac.in>
syzbot has pointed to a possible null pointer dereference in
pfnmap_lockdep_assert. vm_file member of vm_area_struct is being
dereferenced without any checks.
This fix returns if vm_file member in vm_area_struct is NULL.
Reported-by: syzbot+093d096417e7038a689b@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=093d096417e7038a689b
---
This bug[1] triggers a general protection fault in follow_pfnmap_start
function. An assertion pfnmap_lockdep_assert inside this function
dereferences vm_file member of vm_area_struct. And panic gets triggered
when vm_file is NULL.
This patch returns from the assertion pfnmap_lockdep_assert if vm_file
is found to be NULL.
[1] https://syzkaller.appspot.com/bug?extid=093d096417e7038a689b
Signed-off-by: Manas <manas18244@iiitd.ac.in>
---
Changes in v2:
- v2: use ternary operator according to feedback
- Link to v1: https://lore.kernel.org/r/20241003-fix-null-deref-v1-1-0a45df9d016a@iiitd.ac.in
---
mm/memory.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/memory.c b/mm/memory.c
index 2366578015ad..5ed109a8f02e 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -6346,7 +6346,7 @@ static inline void pfnmap_args_setup(struct follow_pfnmap_args *args,
static inline void pfnmap_lockdep_assert(struct vm_area_struct *vma)
{
#ifdef CONFIG_LOCKDEP
- struct address_space *mapping = vma->vm_file->f_mapping;
+ struct address_space *mapping = vma->vm_file ? vma->vm_file->f_mapping : NULL;
if (mapping)
lockdep_assert(lockdep_is_held(&vma->vm_file->f_mapping->i_mmap_rwsem) ||
---
base-commit: 9852d85ec9d492ebef56dc5f229416c925758edc
change-id: 20241003-fix-null-deref-6bfa0337efc3
Best regards,
--
Manas <manas18244@iiitd.ac.in>
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH v2] Fixes: null pointer dereference in pfnmap_lockdep_assert
2024-10-04 13:05 [PATCH v2] Fixes: null pointer dereference in pfnmap_lockdep_assert Manas via B4 Relay
@ 2024-10-04 13:21 ` Peter Xu
2024-10-04 13:27 ` Manas
0 siblings, 1 reply; 3+ messages in thread
From: Peter Xu @ 2024-10-04 13:21 UTC (permalink / raw)
To: manas18244
Cc: Andrew Morton, Shuah Khan, Anup Sharma, linux-mm, linux-kernel,
syzbot+093d096417e7038a689b
On Fri, Oct 04, 2024 at 06:35:53PM +0530, Manas via B4 Relay wrote:
> From: Manas <manas18244@iiitd.ac.in>
>
> syzbot has pointed to a possible null pointer dereference in
> pfnmap_lockdep_assert. vm_file member of vm_area_struct is being
> dereferenced without any checks.
>
> This fix returns if vm_file member in vm_area_struct is NULL.
>
> Reported-by: syzbot+093d096417e7038a689b@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=093d096417e7038a689b
> ---
> This bug[1] triggers a general protection fault in follow_pfnmap_start
> function. An assertion pfnmap_lockdep_assert inside this function
> dereferences vm_file member of vm_area_struct. And panic gets triggered
> when vm_file is NULL.
>
> This patch returns from the assertion pfnmap_lockdep_assert if vm_file
> is found to be NULL.
>
> [1] https://syzkaller.appspot.com/bug?extid=093d096417e7038a689b
>
> Signed-off-by: Manas <manas18244@iiitd.ac.in>
Reviewed-by: Peter Xu <peterx@redhat.com>
One nitpick:
> ---
> Changes in v2:
> - v2: use ternary operator according to feedback
> - Link to v1: https://lore.kernel.org/r/20241003-fix-null-deref-v1-1-0a45df9d016a@iiitd.ac.in
> ---
> mm/memory.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index 2366578015ad..5ed109a8f02e 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -6346,7 +6346,7 @@ static inline void pfnmap_args_setup(struct follow_pfnmap_args *args,
> static inline void pfnmap_lockdep_assert(struct vm_area_struct *vma)
> {
> #ifdef CONFIG_LOCKDEP
> - struct address_space *mapping = vma->vm_file->f_mapping;
> + struct address_space *mapping = vma->vm_file ? vma->vm_file->f_mapping : NULL;
>
> if (mapping)
> lockdep_assert(lockdep_is_held(&vma->vm_file->f_mapping->i_mmap_rwsem) ||
This can use "mapping" directly, as I mentioned in previous email (but
probably got overlooked..).
Thanks!
>
> ---
> base-commit: 9852d85ec9d492ebef56dc5f229416c925758edc
> change-id: 20241003-fix-null-deref-6bfa0337efc3
>
> Best regards,
> --
> Manas <manas18244@iiitd.ac.in>
>
>
--
Peter Xu
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH v2] Fixes: null pointer dereference in pfnmap_lockdep_assert
2024-10-04 13:21 ` Peter Xu
@ 2024-10-04 13:27 ` Manas
0 siblings, 0 replies; 3+ messages in thread
From: Manas @ 2024-10-04 13:27 UTC (permalink / raw)
To: Peter Xu
Cc: Andrew Morton, Shuah Khan, Anup Sharma, linux-mm, linux-kernel,
syzbot+093d096417e7038a689b
On 04.10.2024 09:21, Peter Xu wrote:
>On Fri, Oct 04, 2024 at 06:35:53PM +0530, Manas via B4 Relay wrote:
>> From: Manas <manas18244@iiitd.ac.in>
>>
>> syzbot has pointed to a possible null pointer dereference in
>> pfnmap_lockdep_assert. vm_file member of vm_area_struct is being
>> dereferenced without any checks.
>>
>> This fix returns if vm_file member in vm_area_struct is NULL.
>>
>> Reported-by: syzbot+093d096417e7038a689b@syzkaller.appspotmail.com
>> Closes: https://syzkaller.appspot.com/bug?extid=093d096417e7038a689b
>> ---
>> This bug[1] triggers a general protection fault in follow_pfnmap_start
>> function. An assertion pfnmap_lockdep_assert inside this function
>> dereferences vm_file member of vm_area_struct. And panic gets triggered
>> when vm_file is NULL.
>>
>> This patch returns from the assertion pfnmap_lockdep_assert if vm_file
>> is found to be NULL.
>>
>> [1] https://syzkaller.appspot.com/bug?extid=093d096417e7038a689b
>>
>> Signed-off-by: Manas <manas18244@iiitd.ac.in>
>
>Reviewed-by: Peter Xu <peterx@redhat.com>
>
>One nitpick:
>
>> ---
>> Changes in v2:
>> - v2: use ternary operator according to feedback
>> - Link to v1: https://lore.kernel.org/r/20241003-fix-null-deref-v1-1-0a45df9d016a@iiitd.ac.in
>> ---
>> mm/memory.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/mm/memory.c b/mm/memory.c
>> index 2366578015ad..5ed109a8f02e 100644
>> --- a/mm/memory.c
>> +++ b/mm/memory.c
>> @@ -6346,7 +6346,7 @@ static inline void pfnmap_args_setup(struct follow_pfnmap_args *args,
>> static inline void pfnmap_lockdep_assert(struct vm_area_struct *vma)
>> {
>> #ifdef CONFIG_LOCKDEP
>> - struct address_space *mapping = vma->vm_file->f_mapping;
>> + struct address_space *mapping = vma->vm_file ? vma->vm_file->f_mapping : NULL;
>>
>> if (mapping)
>> lockdep_assert(lockdep_is_held(&vma->vm_file->f_mapping->i_mmap_rwsem) ||
>
>This can use "mapping" directly, as I mentioned in previous email (but
>probably got overlooked..).
>
>Thanks!
Oh no! I missed it. Sending v3...
>
>>
>> ---
>> base-commit: 9852d85ec9d492ebef56dc5f229416c925758edc
>> change-id: 20241003-fix-null-deref-6bfa0337efc3
>>
>> Best regards,
>> --
>> Manas <manas18244@iiitd.ac.in>
>>
>>
>
>--
>Peter Xu
>
--
Manas
^ permalink raw reply [flat|nested] 3+ messages in thread
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2024-10-04 13:05 [PATCH v2] Fixes: null pointer dereference in pfnmap_lockdep_assert Manas via B4 Relay
2024-10-04 13:21 ` Peter Xu
2024-10-04 13:27 ` Manas
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