On Thu, 3 Mar 2022 12:18:24 +, Daniel Thompson wrote:
> On Thu, Mar 03, 2022 at 03:26:57PM +0800, Xiaomeng Tong wrote:
> > On Thu, 3 Mar 2022 04:58:23 +, David Laight wrote:
> > > on 3 Mar 2022 10:27:29 +0800, Xiaomeng Tong wrote:
> > > > The problem is the mis-use of iterator outside the
> From: Xiaomeng Tong
> > Sent: 03 March 2022 07:27
> >
> > On Thu, 3 Mar 2022 04:58:23 +, David Laight wrote:
> > > on 3 Mar 2022 10:27:29 +0800, Xiaomeng Tong wrote:
> > > > The problem is the mis-use of iterator outside the loop on exit, and
> > > > the iterator will be the HEAD's
On Wed, Mar 02, 2022 at 10:29:31AM +0100, Rasmus Villemoes wrote:
> This won't help the current issue (because it doesn't exist and might
> never), but just in case some compiler people are listening, I'd like to
> have some sort of way to tell the compiler "treat this variable as
> uninitialized
From: Xiaomeng Tong
> Sent: 03 March 2022 07:27
>
> On Thu, 3 Mar 2022 04:58:23 +, David Laight wrote:
> > on 3 Mar 2022 10:27:29 +0800, Xiaomeng Tong wrote:
> > > The problem is the mis-use of iterator outside the loop on exit, and
> > > the iterator will be the HEAD's container_of pointer
On Wed, Mar 02, 2022 at 12:07:04PM -0800, Kees Cook wrote:
> On Wed, Mar 02, 2022 at 10:29:31AM +0100, Rasmus Villemoes wrote:
> > This won't help the current issue (because it doesn't exist and might
> > never), but just in case some compiler people are listening, I'd like to
> > have some sort
correct for typo:
-for (struct list_head *list = head->next, cond = (struct list_head *)-1; cond
== (struct list_head *)-1; cond = NULL) \
+for (struct list_head *list = head->next, *cond = (struct list_head *)-1; cond
== (struct list_head *)-1; cond = NULL) \
--
Xiaomeng Tong
> I think this would make sense, it would mean you only assign the containing
> element on valid elements.
>
> I was thinking something along the lines of:
>
> #define list_for_each_entry(pos, head, member)
> \
> for (struct list_head *list =
> On 3. Mar 2022, at 05:58, David Laight wrote:
>
> From: Xiaomeng Tong
>> Sent: 03 March 2022 02:27
>>
>> On Wed, 2 Mar 2022 14:04:06 +, David Laight
>> wrote:
>>> I think that it would be better to make any alternate loop macro
>>> just set the variable to NULL on the loop exit.
>>>
On Thu, 3 Mar 2022 04:58:23 +, David Laight wrote:
> on 3 Mar 2022 10:27:29 +0800, Xiaomeng Tong wrote:
> > The problem is the mis-use of iterator outside the loop on exit, and
> > the iterator will be the HEAD's container_of pointer which pointers
> > to a type-confused struct. Sidenote: The
From: Xiaomeng Tong
> Sent: 03 March 2022 02:27
>
> On Wed, 2 Mar 2022 14:04:06 +, David Laight
> wrote:
> > I think that it would be better to make any alternate loop macro
> > just set the variable to NULL on the loop exit.
> > That is easier to code for and the compiler might be persuaded
On Wed, 2 Mar 2022 14:04:06 +, David Laight
wrote:
> I think that it would be better to make any alternate loop macro
> just set the variable to NULL on the loop exit.
> That is easier to code for and the compiler might be persuaded to
> not redo the test.
No, that would lead to a NULL
On Wed, Mar 02, 2022 at 12:18:45PM -0800, Linus Torvalds wrote:
> On Wed, Mar 2, 2022 at 12:07 PM Kees Cook wrote:
> >
> > I've long wanted to change kfree() to explicitly set pointers to NULL on
> > free. https://github.com/KSPP/linux/issues/87
>
> We've had this discussion with the gcc people
On Wed, Mar 2, 2022 at 12:07 PM Kees Cook wrote:
>
> I've long wanted to change kfree() to explicitly set pointers to NULL on
> free. https://github.com/KSPP/linux/issues/87
We've had this discussion with the gcc people in the past, and gcc
actually has some support for it, but it's sadly tied
On Wed, Mar 02, 2022 at 10:29:31AM +0100, Rasmus Villemoes wrote:
> This won't help the current issue (because it doesn't exist and might
> never), but just in case some compiler people are listening, I'd like to
> have some sort of way to tell the compiler "treat this variable as
> uninitialized
From: Xiaomeng Tong
> Sent: 02 March 2022 09:31
>
> On Mon, 28 Feb 2022 16:41:04 -0800, Linus Torvalds
> wrote:
> >
> > But basically to _me_, the important part is that the end result is
> > maintainable longer-term.
>
> I couldn't agree more. And because of that, I stick with the following
>
On Mon, 28 Feb 2022 16:41:04 -0800, Linus Torvalds
wrote:
>
> But basically to _me_, the important part is that the end result is
> maintainable longer-term.
I couldn't agree more. And because of that, I stick with the following
approach because it's maintainable longer-term than "type(pos) pos"
On 02/03/2022 00.55, Linus Torvalds wrote:
> On Tue, Mar 1, 2022 at 3:19 PM David Laight wrote:
>>
> With the "don't use iterator outside the loop" approach, the exact
> same code works in both the old world order and the new world order,
> and you don't have the semantic confusion. And *if* you
On Tue, Mar 1, 2022 at 3:19 PM David Laight wrote:
>
> Having said that there are so few users of list_entry_is_head()
> it is reasonable to generate two new names.
Well, the problem is that the users of list_entry_is_head() may be few
- but there are a number of _other_ ways to check "was that
From: Linus Torvalds
> Sent: 01 March 2022 23:03
>
> On Tue, Mar 1, 2022 at 2:58 PM David Laight wrote:
> >
> > Can it be resolved by making:
> > #define list_entry_is_head(pos, head, member) ((pos) == NULL)
> > and double-checking that it isn't used anywhere else (except in
> > the list macros
On Tue, Mar 1, 2022 at 2:58 PM David Laight wrote:
>
> Can it be resolved by making:
> #define list_entry_is_head(pos, head, member) ((pos) == NULL)
> and double-checking that it isn't used anywhere else (except in
> the list macros themselves).
Well, yes, except for the fact that then the name
From: Linus Torvalds
> Sent: 01 March 2022 19:07
> On Mon, Feb 28, 2022 at 2:29 PM James Bottomley
> wrote:
> >
> > However, if the desire is really to poison the loop variable then we
> > can do
> >
> > #define list_for_each_entry(pos, head, member) \
> > for
On Tue, Mar 1, 2022 at 11:06 AM Linus Torvalds
wrote:
>
> So instead of that simple "if (!entry)", we'd effectively have to
> continue to use something that still works with the old world order
> (ie that "if (list_entry_is_head())" model).
Just to prove my point about how this is painful, that
On Mon, Feb 28, 2022 at 2:29 PM James Bottomley
wrote:
>
> However, if the desire is really to poison the loop variable then we
> can do
>
> #define list_for_each_entry(pos, head, member) \
> for (pos = list_first_entry(head, typeof(*pos), member);\
>
On Tue, Mar 01, 2022 at 10:14:07AM -0800, Kees Cook wrote:
> On Mon, Feb 28, 2022 at 04:45:11PM -0800, Linus Torvalds wrote:
> > Really. The "-Wshadow doesn't work on the kernel" is not some new
> > issue, because you have to do completely insane things to the source
> > code to enable it.
>
>
On Tue, Mar 1, 2022 at 10:14 AM Kees Cook wrote:
>
> The first big glitch with -Wshadow was with shadowed global variables.
> GCC 4.8 fixed that, but it still yells about shadowed functions. What
> _almost_ works is -Wshadow=local.
Heh. Yeah, I just have long memories of "-Wshadow was a
On Tue, Mar 01, 2022 at 12:28:15PM +0100, Jakob Koschel wrote:
> Based on the coccinelle script there are ~480 cases that need fixing
> in total. I'll now finish all of them and then split them by
> submodules as Greg suggested and repost a patch set per submodule.
> Sounds good?
To help with
On Mon, Feb 28, 2022 at 04:45:11PM -0800, Linus Torvalds wrote:
> Really. The "-Wshadow doesn't work on the kernel" is not some new
> issue, because you have to do completely insane things to the source
> code to enable it.
The first big glitch with -Wshadow was with shadowed global variables.
On Tue, Mar 01, 2022 at 06:40:04PM +0100, Jakob Koschel wrote:
>
>
> > On 1. Mar 2022, at 18:36, Greg KH wrote:
> >
> > On Tue, Mar 01, 2022 at 12:28:15PM +0100, Jakob Koschel wrote:
> >>
> >>
> >>> On 1. Mar 2022, at 01:41, Linus Torvalds
> >>> wrote:
> >>>
> >>> On Mon, Feb 28, 2022 at
On Tue, Mar 01, 2022 at 12:28:15PM +0100, Jakob Koschel wrote:
>
>
> > On 1. Mar 2022, at 01:41, Linus Torvalds
> > wrote:
> >
> > On Mon, Feb 28, 2022 at 1:47 PM Jakob Koschel
> > wrote:
> >>
> >> The goal of this is to get compiler warnings right? This would indeed be
> >> great.
> >
>
> On 1. Mar 2022, at 18:36, Greg KH wrote:
>
> On Tue, Mar 01, 2022 at 12:28:15PM +0100, Jakob Koschel wrote:
>>
>>
>>> On 1. Mar 2022, at 01:41, Linus Torvalds
>>> wrote:
>>>
>>> On Mon, Feb 28, 2022 at 1:47 PM Jakob Koschel
>>> wrote:
The goal of this is to get compiler
On Mon, Feb 28, 2022 at 01:06:57PM +0100, Jakob Koschel wrote:
>
>
> > On 28. Feb 2022, at 12:20, Greg KH wrote:
> >
> > On Mon, Feb 28, 2022 at 12:08:18PM +0100, Jakob Koschel wrote:
> >> If the list does not contain the expected element, the value of
> >> list_for_each_entry() iterator will
> On 1. Mar 2022, at 01:41, Linus Torvalds
> wrote:
>
> On Mon, Feb 28, 2022 at 1:47 PM Jakob Koschel wrote:
>>
>> The goal of this is to get compiler warnings right? This would indeed be
>> great.
>
> Yes, so I don't mind having a one-time patch that has been gathered
> using some
Am 28.02.22 um 22:13 schrieb James Bottomley:
On Mon, 2022-02-28 at 21:56 +0100, Christian König wrote:
Am 28.02.22 um 21:42 schrieb James Bottomley:
On Mon, 2022-02-28 at 21:07 +0100, Christian König wrote:
Am 28.02.22 um 20:56 schrieb Linus Torvalds:
On Mon, Feb 28, 2022 at 4:19 AM
On Mon, 28 Feb 2022 16:41:04 -0800 Linus Torvalds wrote:
> So yes, initially my idea had been to just move the iterator entirely
> inside the macro. But specifying the type got so ugly that I think
> that
>
> typeof (pos) pos
>
> trick inside the macro really ends up giving us the best
From: Matthew Wilcox
> Sent: 28 February 2022 20:16
>
> On Mon, Feb 28, 2022 at 12:10:24PM -0800, Linus Torvalds wrote:
> > We can do
> >
> > typeof(pos) pos
> >
> > in the 'for ()' loop, and never use __iter at all.
> >
> > That means that inside the for-loop, we use a _different_ 'pos'
From: Linus Torvalds
> Sent: 28 February 2022 19:56
> On Mon, Feb 28, 2022 at 4:19 AM Christian König
> wrote:
> >
> > I don't think that using the extra variable makes the code in any way
> > more reliable or easier to read.
>
> So I think the next step is to do the attached patch (which
On Mon, Feb 28, 2022 at 4:45 PM Linus Torvalds
wrote:
>
> Yeah, except that's ugly beyond belief, plus it's literally not what
> we do in the kernel.
(Of course, I probably shouldn't have used 'min()' as an example,
because that is actually one of the few places where we do exactly
that, using
On Mon, Feb 28, 2022 at 4:38 PM Segher Boessenkool
wrote:
>
> In C its scope is the rest of the declaration and the entire loop, not
> anything after it. This was the same in C++98 already, btw (but in
> pre-standard versions of C++ things were like you remember, yes, and it
> was painful).
On Mon, Feb 28, 2022 at 3:26 PM Matthew Wilcox wrote:
>
> #define ___PASTE(a, b) a##b
> #define __PASTE(a, b) ___PASTE(a, b)
> #define _min(a, b, u) ({ \
Yeah, except that's ugly beyond belief, plus it's literally not what
we do in the kernel.
Really. The "-Wshadow doesn't work on the
On Mon, Feb 28, 2022 at 05:28:58PM -0500, James Bottomley wrote:
> On Mon, 2022-02-28 at 23:59 +0200, Mike Rapoport wrote:
> >
> > On February 28, 2022 10:42:53 PM GMT+02:00, James Bottomley <
> > james.bottom...@hansenpartnership.com> wrote:
> > > On Mon, 2022-02-28 at 21:07 +0100, Christian
On Mon, Feb 28, 2022 at 1:47 PM Jakob Koschel wrote:
>
> The goal of this is to get compiler warnings right? This would indeed be
> great.
Yes, so I don't mind having a one-time patch that has been gathered
using some automated checker tool, but I don't think that works from a
long-term
On Mon, Feb 28, 2022 at 12:37:15PM -0800, Linus Torvalds wrote:
> On Mon, Feb 28, 2022 at 12:16 PM Matthew Wilcox wrote:
> >
> > Then we can never use -Wshadow ;-( I'd love to be able to turn it on;
> > it catches real bugs.
>
> Oh, we already can never use -Wshadow regardless of things like
On Mon, 2022-02-28 at 23:59 +0200, Mike Rapoport wrote:
>
> On February 28, 2022 10:42:53 PM GMT+02:00, James Bottomley <
> james.bottom...@hansenpartnership.com> wrote:
> > On Mon, 2022-02-28 at 21:07 +0100, Christian König wrote:
[...]
> > > > I do wish we could actually poison the 'pos' value
> On 28. Feb 2022, at 21:56, Christian König wrote:
>
>
>
> Am 28.02.22 um 21:42 schrieb James Bottomley:
>> On Mon, 2022-02-28 at 21:07 +0100, Christian König wrote:
>>> Am 28.02.22 um 20:56 schrieb Linus Torvalds:
On Mon, Feb 28, 2022 at 4:19 AM Christian König
wrote:
On February 28, 2022 10:42:53 PM GMT+02:00, James Bottomley
wrote:
>On Mon, 2022-02-28 at 21:07 +0100, Christian König wrote:
>> Am 28.02.22 um 20:56 schrieb Linus Torvalds:
>> > On Mon, Feb 28, 2022 at 4:19 AM Christian König
>> > wrote:
>> > > I don't think that using the extra variable
> On 28. Feb 2022, at 21:10, Linus Torvalds
> wrote:
>
> On Mon, Feb 28, 2022 at 12:03 PM Linus Torvalds
> wrote:
>>
>> Side note: we do need *some* way to do it.
>
> Ooh.
>
> This patch is a work of art.
>
> And I mean that in the worst possible way.
>
> We can do
>
>
On Mon, Feb 28, 2022 at 3:45 PM James Bottomley
wrote:
> ...
> > Just from skimming over the patches to change this and experience
> > with the drivers/subsystems I help to maintain I think the primary
> > pattern looks something like this:
> >
> > list_for_each_entry(entry, head, member) {
> >
On Mon, 2022-02-28 at 20:16 +, Matthew Wilcox wrote:
> On Mon, Feb 28, 2022 at 12:10:24PM -0800, Linus Torvalds wrote:
> > We can do
> >
> > typeof(pos) pos
> >
> > in the 'for ()' loop, and never use __iter at all.
> >
> > That means that inside the for-loop, we use a _different_
On Mon, 2022-02-28 at 21:56 +0100, Christian König wrote:
>
> Am 28.02.22 um 21:42 schrieb James Bottomley:
> > On Mon, 2022-02-28 at 21:07 +0100, Christian König wrote:
> > > Am 28.02.22 um 20:56 schrieb Linus Torvalds:
> > > > On Mon, Feb 28, 2022 at 4:19 AM Christian König
> > > > wrote:
> >
On Mon, Feb 28, 2022 at 12:14:44PM -0800, Linus Torvalds wrote:
> On Mon, Feb 28, 2022 at 12:10 PM Linus Torvalds
> wrote:
> >
> > We can do
> >
> > typeof(pos) pos
> >
> > in the 'for ()' loop, and never use __iter at all.
> >
> > That means that inside the for-loop, we use a _different_
Am 28.02.22 um 21:42 schrieb James Bottomley:
On Mon, 2022-02-28 at 21:07 +0100, Christian König wrote:
Am 28.02.22 um 20:56 schrieb Linus Torvalds:
On Mon, Feb 28, 2022 at 4:19 AM Christian König
wrote:
[SNIP]
Anybody have any ideas?
I think we should look at the use cases why code is
On Mon, 2022-02-28 at 21:07 +0100, Christian König wrote:
> Am 28.02.22 um 20:56 schrieb Linus Torvalds:
> > On Mon, Feb 28, 2022 at 4:19 AM Christian König
> > wrote:
> > > I don't think that using the extra variable makes the code in any
> > > way
> > > more reliable or easier to read.
> > So I
On Mon, Feb 28, 2022 at 12:29 PM Johannes Berg
wrote:
>
> If we're willing to change the API for the macro, we could do
>
> list_for_each_entry(type, pos, head, member)
>
> and then actually take advantage of -Wshadow?
See my reply to Willy. There is no way -Wshadow will ever happen.
I
On Mon, Feb 28, 2022 at 12:16 PM Matthew Wilcox wrote:
>
> Then we can never use -Wshadow ;-( I'd love to be able to turn it on;
> it catches real bugs.
Oh, we already can never use -Wshadow regardless of things like this.
That bridge hasn't just been burned, it never existed in the first
On Mon, Feb 28, 2022 at 11:56 AM Linus Torvalds
wrote:
>
> I do wish we could actually poison the 'pos' value after the loop
> somehow - but clearly the "might be uninitialized" I was hoping for
> isn't the way to do it.
Side note: we do need *some* way to do it.
Because if we make that change,
On Mon, Feb 28, 2022 at 12:10 PM Linus Torvalds
wrote:
>
> We can do
>
> typeof(pos) pos
>
> in the 'for ()' loop, and never use __iter at all.
>
> That means that inside the for-loop, we use a _different_ 'pos' than outside.
The thing that makes me throw up in my mouth a bit is that in
On Mon, Feb 28, 2022 at 12:10:24PM -0800, Linus Torvalds wrote:
> We can do
>
> typeof(pos) pos
>
> in the 'for ()' loop, and never use __iter at all.
>
> That means that inside the for-loop, we use a _different_ 'pos' than outside.
Then we can never use -Wshadow ;-( I'd love to be
On Mon, Feb 28, 2022 at 12:03 PM Linus Torvalds
wrote:
>
> Side note: we do need *some* way to do it.
Ooh.
This patch is a work of art.
And I mean that in the worst possible way.
We can do
typeof(pos) pos
in the 'for ()' loop, and never use __iter at all.
That means that inside the
Am 28.02.22 um 20:56 schrieb Linus Torvalds:
On Mon, Feb 28, 2022 at 4:19 AM Christian König
wrote:
I don't think that using the extra variable makes the code in any way
more reliable or easier to read.
So I think the next step is to do the attached patch (which requires
that "-std=gnu11"
On Mon, Feb 28, 2022 at 4:19 AM Christian König
wrote:
>
> I don't think that using the extra variable makes the code in any way
> more reliable or easier to read.
So I think the next step is to do the attached patch (which requires
that "-std=gnu11" that was discussed in the original thread).
On Mon, Feb 28, 2022 at 12:08:18PM +0100, Jakob Koschel wrote:
> diff --git a/drivers/scsi/scsi_transport_sas.c
> b/drivers/scsi/scsi_transport_sas.c
> index 4ee578b181da..a8cbd90db9d2 100644
> --- a/drivers/scsi/scsi_transport_sas.c
> +++ b/drivers/scsi/scsi_transport_sas.c
> @@ -1060,26
> On 28. Feb 2022, at 12:20, Greg KH wrote:
>
> On Mon, Feb 28, 2022 at 12:08:18PM +0100, Jakob Koschel wrote:
>> If the list does not contain the expected element, the value of
>> list_for_each_entry() iterator will not point to a valid structure.
>> To avoid type confusion in such case, the
Am 28.02.22 um 12:08 schrieb Jakob Koschel:
If the list does not contain the expected element, the value of
list_for_each_entry() iterator will not point to a valid structure.
To avoid type confusion in such case, the list iterator
scope will be limited to list_for_each_entry() loop.
We
On Mon, Feb 28, 2022 at 12:08:18PM +0100, Jakob Koschel wrote:
> If the list does not contain the expected element, the value of
> list_for_each_entry() iterator will not point to a valid structure.
> To avoid type confusion in such case, the list iterator
> scope will be limited to
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