2021-03-11 10:38:18

by Shubhankar Kuranagatti

[permalink] [raw]
Subject: [PATCH 1/2] net: core: datagram.c: Fix use of assignment in if condition

The assignment inside the if condition has been changed to
initialising outside the if condition.

Signed-off-by: Shubhankar Kuranagatti <[email protected]>
---
net/core/datagram.c | 31 ++++++++++++++++++++-----------
1 file changed, 20 insertions(+), 11 deletions(-)

diff --git a/net/core/datagram.c b/net/core/datagram.c
index 15ab9ffb27fe..7b2204f102b7 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -427,7 +427,8 @@ static int __skb_datagram_iter(const struct sk_buff *skb, int offset,
offset += n;
if (n != copy)
goto short_copy;
- if ((len -= copy) == 0)
+ len -= copy
+ if ((len) == 0)
return 0;
}

@@ -439,7 +440,8 @@ static int __skb_datagram_iter(const struct sk_buff *skb, int offset,
WARN_ON(start > offset + len);

end = start + skb_frag_size(frag);
- if ((copy = end - offset) > 0) {
+ copy = end - offset
+ if ((copy) > 0) {
struct page *page = skb_frag_page(frag);
u8 *vaddr = kmap(page);

@@ -452,7 +454,8 @@ static int __skb_datagram_iter(const struct sk_buff *skb, int offset,
offset += n;
if (n != copy)
goto short_copy;
- if (!(len -= copy))
+ len -= copy
+ if (!(len))
return 0;
}
start = end;
@@ -464,13 +467,15 @@ static int __skb_datagram_iter(const struct sk_buff *skb, int offset,
WARN_ON(start > offset + len);

end = start + frag_iter->len;
- if ((copy = end - offset) > 0) {
+ copy = end - offset;
+ if ((copy) > 0) {
if (copy > len)
copy = len;
if (__skb_datagram_iter(frag_iter, offset - start,
to, copy, fault_short, cb, data))
goto fault;
- if ((len -= copy) == 0)
+ len -= copy
+ if ((len) == 0)
return 0;
offset += copy;
}
@@ -558,7 +563,8 @@ int skb_copy_datagram_from_iter(struct sk_buff *skb, int offset,
copy = len;
if (copy_from_iter(skb->data + offset, copy, from) != copy)
goto fault;
- if ((len -= copy) == 0)
+ len -= copy;
+ if ((len) == 0)
return 0;
offset += copy;
}
@@ -571,7 +577,8 @@ int skb_copy_datagram_from_iter(struct sk_buff *skb, int offset,
WARN_ON(start > offset + len);

end = start + skb_frag_size(frag);
- if ((copy = end - offset) > 0) {
+ copy = end - offset;
+ if ((copy) > 0) {
size_t copied;

if (copy > len)
@@ -581,8 +588,8 @@ int skb_copy_datagram_from_iter(struct sk_buff *skb, int offset,
copy, from);
if (copied != copy)
goto fault;
-
- if (!(len -= copy))
+ len -= copy
+ if (!(len))
return 0;
offset += copy;
}
@@ -595,14 +602,16 @@ int skb_copy_datagram_from_iter(struct sk_buff *skb, int offset,
WARN_ON(start > offset + len);

end = start + frag_iter->len;
- if ((copy = end - offset) > 0) {
+ copy = end - offset;
+ if ((copy) > 0) {
if (copy > len)
copy = len;
if (skb_copy_datagram_from_iter(frag_iter,
offset - start,
from, copy))
goto fault;
- if ((len -= copy) == 0)
+ len -= copy;
+ if ((len) == 0)
return 0;
offset += copy;
}
--
2.17.1


2021-03-11 11:04:07

by Eric Dumazet

[permalink] [raw]
Subject: Re: [PATCH 1/2] net: core: datagram.c: Fix use of assignment in if condition

On Thu, Mar 11, 2021 at 11:34 AM Shubhankar Kuranagatti
<[email protected]> wrote:
>
> The assignment inside the if condition has been changed to
> initialising outside the if condition.
>
> Signed-off-by: Shubhankar Kuranagatti <[email protected]>
> ---
> net/core/datagram.c | 31 ++++++++++++++++++++-----------
> 1 file changed, 20 insertions(+), 11 deletions(-)
>
> diff --git a/net/core/datagram.c b/net/core/datagram.c
> index 15ab9ffb27fe..7b2204f102b7 100644
> --- a/net/core/datagram.c
> +++ b/net/core/datagram.c
> @@ -427,7 +427,8 @@ static int __skb_datagram_iter(const struct sk_buff *skb, int offset,
> offset += n;
> if (n != copy)
> goto short_copy;
> - if ((len -= copy) == 0)
> + len -= copy
> + if ((len) == 0)
> return 0;
>


Quite frankly I prefer the current style.

It also seems you have not even compiled your change, this is not a good start.

Lets keep reviewer time to review patches that really bring an improvement,
since stylistic changes like that make our backports more likely to
have conflicts.

Thanks.

2021-03-11 15:43:17

by kernel test robot

[permalink] [raw]
Subject: Re: [PATCH 1/2] net: core: datagram.c: Fix use of assignment in if condition

Hi Shubhankar,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on net-next/master]
[also build test ERROR on linus/master v5.12-rc2 next-20210311]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url: https://github.com/0day-ci/linux/commits/Shubhankar-Kuranagatti/net-core-datagram-c-Fix-use-of-assignment-in-if-condition/20210311-184120
base: https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git 34bb975126419e86bc3b95e200dc41de6c6ca69c
config: x86_64-randconfig-r025-20210311 (attached as .config)
compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project 574a9dabc63ba1e7a04c08d4bde2eacd61b44ce1)
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# install x86_64 cross compiling tool for clang build
# apt-get install binutils-x86-64-linux-gnu
# https://github.com/0day-ci/linux/commit/89811231e3ec535f3e5188fb8578535e13c1f1ba
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Shubhankar-Kuranagatti/net-core-datagram-c-Fix-use-of-assignment-in-if-condition/20210311-184120
git checkout 89811231e3ec535f3e5188fb8578535e13c1f1ba
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <[email protected]>

All errors (new ones prefixed by >>):

>> net/core/datagram.c:430:14: error: expected ';' after expression
len -= copy
^
;
net/core/datagram.c:443:22: error: expected ';' after expression
copy = end - offset
^
;
net/core/datagram.c:457:15: error: expected ';' after expression
len -= copy
^
;
net/core/datagram.c:477:15: error: expected ';' after expression
len -= copy
^
;
net/core/datagram.c:591:15: error: expected ';' after expression
len -= copy
^
;
5 errors generated.


vim +430 net/core/datagram.c

406
407 INDIRECT_CALLABLE_DECLARE(static size_t simple_copy_to_iter(const void *addr,
408 size_t bytes,
409 void *data __always_unused,
410 struct iov_iter *i));
411
412 static int __skb_datagram_iter(const struct sk_buff *skb, int offset,
413 struct iov_iter *to, int len, bool fault_short,
414 size_t (*cb)(const void *, size_t, void *,
415 struct iov_iter *), void *data)
416 {
417 int start = skb_headlen(skb);
418 int i, copy = start - offset, start_off = offset, n;
419 struct sk_buff *frag_iter;
420
421 /* Copy header. */
422 if (copy > 0) {
423 if (copy > len)
424 copy = len;
425 n = INDIRECT_CALL_1(cb, simple_copy_to_iter,
426 skb->data + offset, copy, data, to);
427 offset += n;
428 if (n != copy)
429 goto short_copy;
> 430 len -= copy
431 if ((len) == 0)
432 return 0;
433 }
434
435 /* Copy paged appendix. Hmm... why does this look so complicated? */
436 for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
437 int end;
438 const skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
439
440 WARN_ON(start > offset + len);
441
442 end = start + skb_frag_size(frag);
443 copy = end - offset
444 if ((copy) > 0) {
445 struct page *page = skb_frag_page(frag);
446 u8 *vaddr = kmap(page);
447
448 if (copy > len)
449 copy = len;
450 n = INDIRECT_CALL_1(cb, simple_copy_to_iter,
451 vaddr + skb_frag_off(frag) + offset - start,
452 copy, data, to);
453 kunmap(page);
454 offset += n;
455 if (n != copy)
456 goto short_copy;
457 len -= copy
458 if (!(len))
459 return 0;
460 }
461 start = end;
462 }
463
464 skb_walk_frags(skb, frag_iter) {
465 int end;
466
467 WARN_ON(start > offset + len);
468
469 end = start + frag_iter->len;
470 copy = end - offset;
471 if ((copy) > 0) {
472 if (copy > len)
473 copy = len;
474 if (__skb_datagram_iter(frag_iter, offset - start,
475 to, copy, fault_short, cb, data))
476 goto fault;
477 len -= copy
478 if ((len) == 0)
479 return 0;
480 offset += copy;
481 }
482 start = end;
483 }
484 if (!len)
485 return 0;
486
487 /* This is not really a user copy fault, but rather someone
488 * gave us a bogus length on the skb. We should probably
489 * print a warning here as it may indicate a kernel bug.
490 */
491
492 fault:
493 iov_iter_revert(to, offset - start_off);
494 return -EFAULT;
495
496 short_copy:
497 if (fault_short || iov_iter_count(to))
498 goto fault;
499
500 return 0;
501 }
502

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/[email protected]


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