[PATCH] gfs2: Fix use-after-free in gfs2_remove_from_journal()

[PATCH] gfs2: Fix use-after-free in gfs2_remove_from_journal()

[Hongling Zeng]

The function calls brelse(bh) but then continues to access
the buffer head through bh->b_private, clear_buffer_dirty(),
and clear_buffer_uptodate().

After brelse() decreases the reference count, the buffer head
may be freed, making the subsequent accesses use-after-free.

Fix by moving the brelse(bh) call to the end of the function,
after all accesses to bh have been completed.

Fixes: e93b100931a4 ("GFS2: Fix slab memory leak in gfs2_bufdata")
Signed-off-by: Hongling Zeng <zenghongling@kylinos.cn>
---
 fs/gfs2/log.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index 78bba8cc10b8..a92c84146de9 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -1038,7 +1038,6 @@ void gfs2_remove_from_journal(struct buffer_head *bh, int meta)
 			set_bit(TR_TOUCHED, &tr->tr_flags);
 		}
 		was_pinned = 1;
-		brelse(bh);
 	}
 	if (bd) {
 		if (bd->bd_tr) {
@@ -1056,6 +1055,8 @@ void gfs2_remove_from_journal(struct buffer_head *bh, int meta)
 	}
 	clear_buffer_dirty(bh);
 	clear_buffer_uptodate(bh);
+	if (was_pinned)
+		brelse(bh);
 }
 
 /**
-- 
2.25.1

Re: [PATCH] gfs2: Fix use-after-free in gfs2_remove_from_journal()

[Andrew Price]

On 17/06/2026 10:01, Hongling Zeng wrote:
> The function calls brelse(bh) but then continues to access
> the buffer head through bh->b_private, clear_buffer_dirty(),
> and clear_buffer_uptodate().
> 
> After brelse() decreases the reference count, the buffer head
> may be freed, making the subsequent accesses use-after-free.

When buffers are pinned their refcount is incremented and the brelse() here is only called for pinned buffers so I'm not convinced that there's a bug.

Callers of gfs2_remove_from_journal() also use the bh afterwards so if there was a use-after-free this patch wouldn't fix it.

Did you see a use-after-free in testing?

Andy


> Fix by moving the brelse(bh) call to the end of the function,
> after all accesses to bh have been completed.
> 
> Fixes: e93b100931a4 ("GFS2: Fix slab memory leak in gfs2_bufdata")
> Signed-off-by: Hongling Zeng <zenghongling@kylinos.cn>
> ---
>  fs/gfs2/log.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
> index 78bba8cc10b8..a92c84146de9 100644
> --- a/fs/gfs2/log.c
> +++ b/fs/gfs2/log.c
> @@ -1038,7 +1038,6 @@ void gfs2_remove_from_journal(struct buffer_head *bh, int meta)
>  			set_bit(TR_TOUCHED, &tr->tr_flags);
>  		}
>  		was_pinned = 1;
> -		brelse(bh);
>  	}
>  	if (bd) {
>  		if (bd->bd_tr) {
> @@ -1056,6 +1055,8 @@ void gfs2_remove_from_journal(struct buffer_head *bh, int meta)
>  	}
>  	clear_buffer_dirty(bh);
>  	clear_buffer_uptodate(bh);
> +	if (was_pinned)
> +		brelse(bh);
>  }
>  
>  /**

Re: [PATCH] gfs2: Fix use-after-free in gfs2_remove_from_journal()

[Hongling Zeng]

在 2026年06月17日 18:51, Andrew Price 写道:
> On 17/06/2026 10:01, Hongling Zeng wrote:
>> The function calls brelse(bh) but then continues to access
>> the buffer head through bh->b_private, clear_buffer_dirty(),
>> and clear_buffer_uptodate().
>>
>> After brelse() decreases the reference count, the buffer head
>> may be freed, making the subsequent accesses use-after-free.
> When buffers are pinned their refcount is incremented and the brelse() here is only called for pinned buffers so I'm not convinced that there's a bug.
>
> Callers of gfs2_remove_from_journal() also use the bh afterwards so if there was a use-after-free this patch wouldn't fix it.
>
> Did you see a use-after-free in testing?
>
> Andy
>
  Thanks for your detailed explanation!  this is not a real bug in 
practice, the reference counting protects against real UAF.
  I'm seeing smatch warnings :

       fs/gfs2/log.c:1044 error: dereferencing freed memory 'bh'
       fs/gfs2/log.c:1051 warn: passing freed memory 'bh'

   And there are potential concerns:
   1. Future maintainers might not understand the ref counting semantics
   2. The code pattern (brelse then access) is error-prone
   3. smatch warnings clutter output for real issues
>> Fix by moving the brelse(bh) call to the end of the function,
>> after all accesses to bh have been completed.
>>
>> Fixes: e93b100931a4 ("GFS2: Fix slab memory leak in gfs2_bufdata")
>> Signed-off-by: Hongling Zeng <zenghongling@kylinos.cn>
>> ---
>>   fs/gfs2/log.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
>> index 78bba8cc10b8..a92c84146de9 100644
>> --- a/fs/gfs2/log.c
>> +++ b/fs/gfs2/log.c
>> @@ -1038,7 +1038,6 @@ void gfs2_remove_from_journal(struct buffer_head *bh, int meta)
>>   			set_bit(TR_TOUCHED, &tr->tr_flags);
>>   		}
>>   		was_pinned = 1;
>> -		brelse(bh);
>>   	}
>>   	if (bd) {
>>   		if (bd->bd_tr) {
>> @@ -1056,6 +1055,8 @@ void gfs2_remove_from_journal(struct buffer_head *bh, int meta)
>>   	}
>>   	clear_buffer_dirty(bh);
>>   	clear_buffer_uptodate(bh);
>> +	if (was_pinned)
>> +		brelse(bh);
>>   }
>>   
>>   /**

Re: [PATCH] gfs2: Fix use-after-free in gfs2_remove_from_journal()

[Andreas Gruenbacher]

Andy,

On Wed, Jun 17, 2026 at 12:52 PM Andrew Price <anprice@redhat.com> wrote:
> On 17/06/2026 10:01, Hongling Zeng wrote:
> > The function calls brelse(bh) but then continues to access
> > the buffer head through bh->b_private, clear_buffer_dirty(),
> > and clear_buffer_uptodate().
> >
> > After brelse() decreases the reference count, the buffer head
> > may be freed, making the subsequent accesses use-after-free.
>
> When buffers are pinned their refcount is incremented and the brelse() here is only called for pinned buffers so I'm not convinced that there's a bug.

Not sure what you mean by that. The patch still only calls brelse() on
buffers it unpins, it only changes when it does it.

> Callers of gfs2_remove_from_journal() also use the bh afterwards so if there was a use-after-free this patch wouldn't fix it.

Do we have any callers that do that when they don't clearly still hold
a reference? I don't think so.

In any case, if there are any callers that don't certainly hold an
extra reference, we need to be careful in gfs2_remove_from_journal().
This patch achieves that, so I'm inclined to merge it.

Thanks,
Andreas

Re: [PATCH] gfs2: Fix use-after-free in gfs2_remove_from_journal()

[Andrew Price]

On 24/08/2026 15:20, Andreas Gruenbacher wrote:
> Andy,
> 
> On Wed, Jun 17, 2026 at 12:52 PM Andrew Price <anprice@redhat.com> wrote:
>> On 17/06/2026 10:01, Hongling Zeng wrote:
>>> The function calls brelse(bh) but then continues to access
>>> the buffer head through bh->b_private, clear_buffer_dirty(),
>>> and clear_buffer_uptodate().
>>>
>>> After brelse() decreases the reference count, the buffer head
>>> may be freed, making the subsequent accesses use-after-free.
>>
>> When buffers are pinned their refcount is incremented and the brelse() here is only called for pinned buffers so I'm not convinced that there's a bug.
> 
> Not sure what you mean by that. The patch still only calls brelse() on
> buffers it unpins, it only changes when it does it.

The context is not fresh in my mind but I suppose was trying to locate the UAF that the patch reportedly fixed and I couldn't find one.

>> Callers of gfs2_remove_from_journal() also use the bh afterwards so if there was a use-after-free this patch wouldn't fix it.
> 
> Do we have any callers that do that when they don't clearly still hold
> a reference? I don't think so.
> 
> In any case, if there are any callers that don't certainly hold an
> extra reference, we need to be careful in gfs2_remove_from_journal().
> This patch achieves that, so I'm inclined to merge it.
No objections here. I'd like the commit description to be clear about whether it's fixing a bug or just cleaning up a static analysis warning.

Andy

Re: [PATCH] gfs2: Fix use-after-free in gfs2_remove_from_journal()

[Andreas Gruenbacher]

Hi Hongling Zeng,

On Thu, Jun 18, 2026 at 3:58 AM Hongling Zeng <zhongling0719@126.com> wrote:
> 在 2026年06月17日 18:51, Andrew Price 写道:
> > On 17/06/2026 10:01, Hongling Zeng wrote:
> >> The function calls brelse(bh) but then continues to access
> >> the buffer head through bh->b_private, clear_buffer_dirty(),
> >> and clear_buffer_uptodate().
> >>
> >> After brelse() decreases the reference count, the buffer head
> >> may be freed, making the subsequent accesses use-after-free.
> > When buffers are pinned their refcount is incremented and the brelse() here is only called for pinned buffers so I'm not convinced that there's a bug.
> >
> > Callers of gfs2_remove_from_journal() also use the bh afterwards so if there was a use-after-free this patch wouldn't fix it.
> >
> > Did you see a use-after-free in testing?
> >
> > Andy
> >
>   Thanks for your detailed explanation!  this is not a real bug in
> practice, the reference counting protects against real UAF.
>   I'm seeing smatch warnings :
>
>        fs/gfs2/log.c:1044 error: dereferencing freed memory 'bh'
>        fs/gfs2/log.c:1051 warn: passing freed memory 'bh'

a "make C=2 CHECK="smatch" fs/gfs2/" doesn't result in those messages.
How can I reproduce?

Thanks,
Andreas

>    And there are potential concerns:
>    1. Future maintainers might not understand the ref counting semantics
>    2. The code pattern (brelse then access) is error-prone
>    3. smatch warnings clutter output for real issues
> >> Fix by moving the brelse(bh) call to the end of the function,
> >> after all accesses to bh have been completed.
> >>
> >> Fixes: e93b100931a4 ("GFS2: Fix slab memory leak in gfs2_bufdata")
> >> Signed-off-by: Hongling Zeng <zenghongling@kylinos.cn>
> >> ---
> >>   fs/gfs2/log.c | 3 ++-
> >>   1 file changed, 2 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
> >> index 78bba8cc10b8..a92c84146de9 100644
> >> --- a/fs/gfs2/log.c
> >> +++ b/fs/gfs2/log.c
> >> @@ -1038,7 +1038,6 @@ void gfs2_remove_from_journal(struct buffer_head *bh, int meta)
> >>                      set_bit(TR_TOUCHED, &tr->tr_flags);
> >>              }
> >>              was_pinned = 1;
> >> -            brelse(bh);
> >>      }
> >>      if (bd) {
> >>              if (bd->bd_tr) {
> >> @@ -1056,6 +1055,8 @@ void gfs2_remove_from_journal(struct buffer_head *bh, int meta)
> >>      }
> >>      clear_buffer_dirty(bh);
> >>      clear_buffer_uptodate(bh);
> >> +    if (was_pinned)
> >> +            brelse(bh);
> >>   }
> >>
> >>   /**
>

Re: [PATCH] gfs2: Fix use-after-free in gfs2_remove_from_journal()

[Andreas Gruenbacher]

On Wed, Jun 17, 2026 at 11:02 AM Hongling Zeng <zenghongling@kylinos.cn> wrote:
> The function calls brelse(bh) but then continues to access
> the buffer head through bh->b_private, clear_buffer_dirty(),
> and clear_buffer_uptodate().
>
> After brelse() decreases the reference count, the buffer head
> may be freed, making the subsequent accesses use-after-free.
>
> Fix by moving the brelse(bh) call to the end of the function,
> after all accesses to bh have been completed.
>
> Fixes: e93b100931a4 ("GFS2: Fix slab memory leak in gfs2_bufdata")

That commit by Bob looks suspicious: bh->b_private data is usually
freed by the ->release_folio address space operation, so there should
be no need for freeing bufdata objects here. (That has little to do
with your commit, of course.)

> Signed-off-by: Hongling Zeng <zenghongling@kylinos.cn>
> ---
>  fs/gfs2/log.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
> index 78bba8cc10b8..a92c84146de9 100644
> --- a/fs/gfs2/log.c
> +++ b/fs/gfs2/log.c
> @@ -1038,7 +1038,6 @@ void gfs2_remove_from_journal(struct buffer_head *bh, int meta)
>                         set_bit(TR_TOUCHED, &tr->tr_flags);
>                 }
>                 was_pinned = 1;
> -               brelse(bh);
>         }
>         if (bd) {
>                 if (bd->bd_tr) {
> @@ -1056,6 +1055,8 @@ void gfs2_remove_from_journal(struct buffer_head *bh, int meta)
>         }
>         clear_buffer_dirty(bh);
>         clear_buffer_uptodate(bh);
> +       if (was_pinned)
> +               brelse(bh);
>  }
>
>  /**
> --
> 2.25.1
>

Re: [PATCH] gfs2: Fix use-after-free in gfs2_remove_from_journal()

[Hongling Zeng]

在 2026年08月24日 23:35, Andreas Gruenbacher 写道:
> Hi Hongling Zeng,
>
> On Thu, Jun 18, 2026 at 3:58 AM Hongling Zeng <zhongling0719@126.com> wrote:
>> 在 2026年06月17日 18:51, Andrew Price 写道:
>>> On 17/06/2026 10:01, Hongling Zeng wrote:
>>>> The function calls brelse(bh) but then continues to access
>>>> the buffer head through bh->b_private, clear_buffer_dirty(),
>>>> and clear_buffer_uptodate().
>>>>
>>>> After brelse() decreases the reference count, the buffer head
>>>> may be freed, making the subsequent accesses use-after-free.
>>> When buffers are pinned their refcount is incremented and the brelse() here is only called for pinned buffers so I'm not convinced that there's a bug.
>>>
>>> Callers of gfs2_remove_from_journal() also use the bh afterwards so if there was a use-after-free this patch wouldn't fix it.
>>>
>>> Did you see a use-after-free in testing?
>>>
>>> Andy
>>>
>>    Thanks for your detailed explanation!  this is not a real bug in
>> practice, the reference counting protects against real UAF.
>>    I'm seeing smatch warnings :
>>
>>         fs/gfs2/log.c:1044 error: dereferencing freed memory 'bh'
>>         fs/gfs2/log.c:1051 warn: passing freed memory 'bh'
> a "make C=2 CHECK="smatch" fs/gfs2/" doesn't result in those messages.
> How can I reproduce?
>
> Thanks,
> Andreas
>
   Hi Andreas and Andy,

   Thank you for the review. The smatch warnings were reported by the Intel
   LKP test robot:

     https://lore.kernel.org/all/202607110908.l7Owhul4-lkp@intel.com/

   I will update the patch with a better commit message based on your 
feedback,
   clarifying that this is a defensive improvement to address the pattern
   flagged by static analysis, rather than fixing a real-world 
use-after-free
   bug.

   I'll send a v2 version .

>>     And there are potential concerns:
>>     1. Future maintainers might not understand the ref counting semantics
>>     2. The code pattern (brelse then access) is error-prone
>>     3. smatch warnings clutter output for real issues
>>>> Fix by moving the brelse(bh) call to the end of the function,
>>>> after all accesses to bh have been completed.
>>>>
>>>> Fixes: e93b100931a4 ("GFS2: Fix slab memory leak in gfs2_bufdata")
>>>> Signed-off-by: Hongling Zeng <zenghongling@kylinos.cn>
>>>> ---
>>>>    fs/gfs2/log.c | 3 ++-
>>>>    1 file changed, 2 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
>>>> index 78bba8cc10b8..a92c84146de9 100644
>>>> --- a/fs/gfs2/log.c
>>>> +++ b/fs/gfs2/log.c
>>>> @@ -1038,7 +1038,6 @@ void gfs2_remove_from_journal(struct buffer_head *bh, int meta)
>>>>                       set_bit(TR_TOUCHED, &tr->tr_flags);
>>>>               }
>>>>               was_pinned = 1;
>>>> -            brelse(bh);
>>>>       }
>>>>       if (bd) {
>>>>               if (bd->bd_tr) {
>>>> @@ -1056,6 +1055,8 @@ void gfs2_remove_from_journal(struct buffer_head *bh, int meta)
>>>>       }
>>>>       clear_buffer_dirty(bh);
>>>>       clear_buffer_uptodate(bh);
>>>> +    if (was_pinned)
>>>> +            brelse(bh);
>>>>    }
>>>>
>>>>    /**

Re: [PATCH] gfs2: Fix use-after-free in gfs2_remove_from_journal()

[Andreas Gruenbacher]

On Tue, Aug 25, 2026 at 3:36 AM Hongling Zeng <zhongling0719@126.com> wrote:
> 在 2026年08月24日 23:35, Andreas Gruenbacher 写道:
> > Hi Hongling Zeng,
> >
> > On Thu, Jun 18, 2026 at 3:58 AM Hongling Zeng <zhongling0719@126.com> wrote:
> >> 在 2026年06月17日 18:51, Andrew Price 写道:
> >>> On 17/06/2026 10:01, Hongling Zeng wrote:
> >>>> The function calls brelse(bh) but then continues to access
> >>>> the buffer head through bh->b_private, clear_buffer_dirty(),
> >>>> and clear_buffer_uptodate().
> >>>>
> >>>> After brelse() decreases the reference count, the buffer head
> >>>> may be freed, making the subsequent accesses use-after-free.
> >>> When buffers are pinned their refcount is incremented and the brelse() here is only called for pinned buffers so I'm not convinced that there's a bug.
> >>>
> >>> Callers of gfs2_remove_from_journal() also use the bh afterwards so if there was a use-after-free this patch wouldn't fix it.
> >>>
> >>> Did you see a use-after-free in testing?
> >>>
> >>> Andy
> >>>
> >>    Thanks for your detailed explanation!  this is not a real bug in
> >> practice, the reference counting protects against real UAF.
> >>    I'm seeing smatch warnings :
> >>
> >>         fs/gfs2/log.c:1044 error: dereferencing freed memory 'bh'
> >>         fs/gfs2/log.c:1051 warn: passing freed memory 'bh'
> > a "make C=2 CHECK="smatch" fs/gfs2/" doesn't result in those messages.
> > How can I reproduce?
> >
> > Thanks,
> > Andreas
> >
>    Hi Andreas and Andy,
>
>    Thank you for the review. The smatch warnings were reported by the Intel
>    LKP test robot:
>
>      https://lore.kernel.org/all/202607110908.l7Owhul4-lkp@intel.com/
>
>    I will update the patch with a better commit message based on your feedback,
>    clarifying that this is a defensive improvement to address the pattern
>    flagged by static analysis, rather than fixing a real-world use-after-free
>    bug.
>
>    I'll send a v2 version.

I still cannot reproduce that result with smatch 0.6.4 (up from
v0.5.0-9185-gbcc58b9c) on Fedora 44, but I can live with this patch.
Thanks!

Andreas

> >>     And there are potential concerns:
> >>     1. Future maintainers might not understand the ref counting semantics
> >>     2. The code pattern (brelse then access) is error-prone
> >>     3. smatch warnings clutter output for real issues
> >>>> Fix by moving the brelse(bh) call to the end of the function,
> >>>> after all accesses to bh have been completed.
> >>>>
> >>>> Fixes: e93b100931a4 ("GFS2: Fix slab memory leak in gfs2_bufdata")
> >>>> Signed-off-by: Hongling Zeng <zenghongling@kylinos.cn>
> >>>> ---
> >>>>    fs/gfs2/log.c | 3 ++-
> >>>>    1 file changed, 2 insertions(+), 1 deletion(-)
> >>>>
> >>>> diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
> >>>> index 78bba8cc10b8..a92c84146de9 100644
> >>>> --- a/fs/gfs2/log.c
> >>>> +++ b/fs/gfs2/log.c
> >>>> @@ -1038,7 +1038,6 @@ void gfs2_remove_from_journal(struct buffer_head *bh, int meta)
> >>>>                       set_bit(TR_TOUCHED, &tr->tr_flags);
> >>>>               }
> >>>>               was_pinned = 1;
> >>>> -            brelse(bh);
> >>>>       }
> >>>>       if (bd) {
> >>>>               if (bd->bd_tr) {
> >>>> @@ -1056,6 +1055,8 @@ void gfs2_remove_from_journal(struct buffer_head *bh, int meta)
> >>>>       }
> >>>>       clear_buffer_dirty(bh);
> >>>>       clear_buffer_uptodate(bh);
> >>>> +    if (was_pinned)
> >>>> +            brelse(bh);
> >>>>    }
> >>>>
> >>>>    /**
>

Re: [PATCH] gfs2: Fix use-after-free in gfs2_remove_from_journal()

[Greg KH]

On Mon, Jun 01, 2026 at 10:18:12AM +0800, Hongling Zeng wrote:
> The function calls brelse(bh) but then continues to access
> the buffer head through bh->b_private, clear_buffer_dirty(),
> and clear_buffer_uptodate().
> 
> After brelse() decreases the reference count, the buffer head
> may be freed, making the subsequent accesses use-after-free.
> 
> Fix by moving the brelse(bh) call to the end of the function,
> after all accesses to bh have been completed.
> 
> Fixes: e93b100931a4 ("GFS2: Fix slab memory leak in gfs2_bufdata")
> Signed-off-by: Hongling Zeng <zenghongling@kylinos.cn>
> ---
>  fs/gfs2/log.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
> index 78bba8cc10b8..a92c84146de9 100644
> --- a/fs/gfs2/log.c
> +++ b/fs/gfs2/log.c
> @@ -1038,7 +1038,6 @@ void gfs2_remove_from_journal(struct buffer_head *bh, int meta)
>  			set_bit(TR_TOUCHED, &tr->tr_flags);
>  		}
>  		was_pinned = 1;
> -		brelse(bh);
>  	}
>  	if (bd) {
>  		if (bd->bd_tr) {
> @@ -1056,6 +1055,8 @@ void gfs2_remove_from_journal(struct buffer_head *bh, int meta)
>  	}
>  	clear_buffer_dirty(bh);
>  	clear_buffer_uptodate(bh);
> +	if (was_pinned)
> +		brelse(bh);
>  }
>  
>  /**
> -- 
> 2.25.1
> 

Hi,

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[PATCH] gfs2: Fix use-after-free in gfs2_remove_from_journal()

[Hongling Zeng]

The function calls brelse(bh) but then continues to access
the buffer head through bh->b_private, clear_buffer_dirty(),
and clear_buffer_uptodate().

After brelse() decreases the reference count, the buffer head
may be freed, making the subsequent accesses use-after-free.

Fix by moving the brelse(bh) call to the end of the function,
after all accesses to bh have been completed.

Fixes: e93b100931a4 ("GFS2: Fix slab memory leak in gfs2_bufdata")
Signed-off-by: Hongling Zeng <zenghongling@kylinos.cn>
---
 fs/gfs2/log.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index 78bba8cc10b8..a92c84146de9 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -1038,7 +1038,6 @@ void gfs2_remove_from_journal(struct buffer_head *bh, int meta)
 			set_bit(TR_TOUCHED, &tr->tr_flags);
 		}
 		was_pinned = 1;
-		brelse(bh);
 	}
 	if (bd) {
 		if (bd->bd_tr) {
@@ -1056,6 +1055,8 @@ void gfs2_remove_from_journal(struct buffer_head *bh, int meta)
 	}
 	clear_buffer_dirty(bh);
 	clear_buffer_uptodate(bh);
+	if (was_pinned)
+		brelse(bh);
 }
 
 /**
-- 
2.25.1

[PATCH] gfs2: Fix use-after-free in gfs2_remove_from_journal()

[Hongling Zeng]

The function calls brelse(bh) but then continues to access
the buffer head through bh->b_private, clear_buffer_dirty(),
and clear_buffer_uptodate().

After brelse() decreases the reference count, the buffer head
may be freed, making the subsequent accesses use-after-free.

Fix by moving the brelse(bh) call to the end of the function,
after all accesses to bh have been completed.

Fixes: e93b100931a4 ("GFS2: Fix slab memory leak in gfs2_bufdata")
Signed-off-by: Hongling Zeng <zenghongling@kylinos.cn>
---
 fs/gfs2/log.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index 78bba8cc10b8..a92c84146de9 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -1038,7 +1038,6 @@ void gfs2_remove_from_journal(struct buffer_head *bh, int meta)
 			set_bit(TR_TOUCHED, &tr->tr_flags);
 		}
 		was_pinned = 1;
-		brelse(bh);
 	}
 	if (bd) {
 		if (bd->bd_tr) {
@@ -1056,6 +1055,8 @@ void gfs2_remove_from_journal(struct buffer_head *bh, int meta)
 	}
 	clear_buffer_dirty(bh);
 	clear_buffer_uptodate(bh);
+	if (was_pinned)
+		brelse(bh);
 }
 
 /**
-- 
2.25.1