* [PATCH] mm/vmalloc.c: check the addr first
@ 2020-09-27 16:33 Hui Su
2020-09-28 18:04 ` Ira Weiny
0 siblings, 1 reply; 3+ messages in thread
From: Hui Su @ 2020-09-27 16:33 UTC (permalink / raw)
To: akpm, linux-mm, linux-kernel
As the comments said, if @addr is NULL, no operation
is performed, check the addr first in vfree() and
vfree_atomic() maybe a better choice.
Signed-off-by: Hui Su <sh_def@163.com>
---
mm/vmalloc.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index be4724b916b3..1cf50749a209 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2305,10 +2305,11 @@ void vfree_atomic(const void *addr)
{
BUG_ON(in_nmi());
- kmemleak_free(addr);
-
if (!addr)
return;
+
+ kmemleak_free(addr);
+
__vfree_deferred(addr);
}
@@ -2340,13 +2341,13 @@ void vfree(const void *addr)
{
BUG_ON(in_nmi());
+ if (!addr)
+ return;
+
kmemleak_free(addr);
might_sleep_if(!in_interrupt());
- if (!addr)
- return;
-
__vfree(addr);
}
EXPORT_SYMBOL(vfree);
--
2.25.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] mm/vmalloc.c: check the addr first
2020-09-27 16:33 [PATCH] mm/vmalloc.c: check the addr first Hui Su
@ 2020-09-28 18:04 ` Ira Weiny
2020-10-08 12:11 ` Hui Su
0 siblings, 1 reply; 3+ messages in thread
From: Ira Weiny @ 2020-09-28 18:04 UTC (permalink / raw)
To: Hui Su; +Cc: akpm, linux-mm, linux-kernel
On Mon, Sep 28, 2020 at 12:33:37AM +0800, Hui Su wrote:
> As the comments said, if @addr is NULL, no operation
> is performed, check the addr first in vfree() and
> vfree_atomic() maybe a better choice.
I don't see how this change helps anything. kmemleak_free() checks addr so no
danger there. Also kmemleak_free() contains a pr_debug() which some might find
useful.
Ira
>
> Signed-off-by: Hui Su <sh_def@163.com>
> ---
> mm/vmalloc.c | 11 ++++++-----
> 1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index be4724b916b3..1cf50749a209 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2305,10 +2305,11 @@ void vfree_atomic(const void *addr)
> {
> BUG_ON(in_nmi());
>
> - kmemleak_free(addr);
> -
> if (!addr)
> return;
> +
> + kmemleak_free(addr);
> +
> __vfree_deferred(addr);
> }
>
> @@ -2340,13 +2341,13 @@ void vfree(const void *addr)
> {
> BUG_ON(in_nmi());
>
> + if (!addr)
> + return;
> +
> kmemleak_free(addr);
>
> might_sleep_if(!in_interrupt());
>
> - if (!addr)
> - return;
> -
> __vfree(addr);
> }
> EXPORT_SYMBOL(vfree);
> --
> 2.25.1
>
>
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] mm/vmalloc.c: check the addr first
2020-09-28 18:04 ` Ira Weiny
@ 2020-10-08 12:11 ` Hui Su
0 siblings, 0 replies; 3+ messages in thread
From: Hui Su @ 2020-10-08 12:11 UTC (permalink / raw)
To: Ira Weiny; +Cc: akpm, linux-mm, linux-kernel
On Mon, Sep 28, 2020 at 11:04:34AM -0700, Ira Weiny wrote:
> On Mon, Sep 28, 2020 at 12:33:37AM +0800, Hui Su wrote:
> > As the comments said, if @addr is NULL, no operation
> > is performed, check the addr first in vfree() and
> > vfree_atomic() maybe a better choice.
>
> I don't see how this change helps anything. kmemleak_free() checks addr so no
> danger there. Also kmemleak_free() contains a pr_debug() which some might find
> useful.
>
> Ira
>
Thanks for your explanations, Ira.
Firstly, as you have said, the kmemleak_free() only unregister a previously
registered object(which shouldn't be NULL), and kmemleak_free() alse check the
ptr whether is NULL, it does no danger here.
Secondly, as you said kmemleak_free() contains a pr_debug() which will be useful,
and i don't think so because this patch only filter out the NULL pointer case, which
may not be useful?(maybe not right?)
Thirdly, let's see kimage_file_prepare_segments() and kimage_file_post_load_cleanup()
in kernel/kexec_file.c.
kimage_file_prepare_segments() uses 'out' label in several places, when reading
files from kernel_fd or initrd_fd or memdup_user cmdline_buf.
The out label will run kimage_file_post_load_cleanup(), which will do vfree()
for ->kernel_buf and ->initrd_buf and ->cmdline_buf and so on...
Supposing the arch_kexec_kernel_image_probe() failed, and it goto out, then it
still vfree(->initrd_buf). In this case we can return faster if we check param
addr first in vfree().
In this case maybe we should use more Precise labels?
All above is my opinion, thanks.
> >
> > Signed-off-by: Hui Su <sh_def@163.com>
> > ---
> > mm/vmalloc.c | 11 ++++++-----
> > 1 file changed, 6 insertions(+), 5 deletions(-)
> >
> > diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> > index be4724b916b3..1cf50749a209 100644
> > --- a/mm/vmalloc.c
> > +++ b/mm/vmalloc.c
> > @@ -2305,10 +2305,11 @@ void vfree_atomic(const void *addr)
> > {
> > BUG_ON(in_nmi());
> >
> > - kmemleak_free(addr);
> > -
> > if (!addr)
> > return;
> > +
> > + kmemleak_free(addr);
> > +
> > __vfree_deferred(addr);
> > }
> >
> > @@ -2340,13 +2341,13 @@ void vfree(const void *addr)
> > {
> > BUG_ON(in_nmi());
> >
> > + if (!addr)
> > + return;
> > +
> > kmemleak_free(addr);
> >
> > might_sleep_if(!in_interrupt());
> >
> > - if (!addr)
> > - return;
> > -
> > __vfree(addr);
> > }
> > EXPORT_SYMBOL(vfree);
> > --
> > 2.25.1
> >
> >
> >
^ permalink raw reply [flat|nested] 3+ messages in thread
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2020-09-27 16:33 [PATCH] mm/vmalloc.c: check the addr first Hui Su
2020-09-28 18:04 ` Ira Weiny
2020-10-08 12:11 ` Hui Su
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