Hi David, Adam,
(2014/06/18 23:43), David Sterba wrote:
On Wed, Jun 18, 2014 at 03:20:30PM +0900, Satoru Takeuchi wrote:
Hi Adam,
(2014/06/14 6:18), Adam Buchbinder wrote:
When running with UndefinedBehaviorSanitizer, the tests produce the following
error:
radix-tree.c:836:30: runtime error: shift exponent 18446744073709551613
is too large for 64-bit type 'unsigned long'
(That's a negative shift exponent represented as an unsigned long.)
Even though the value is discarded in those cases, it's still undefined
behavior; see the C99 standard, section 6.5.7, paragraph three: "If the
value of the right operand is negative [...] the behavior is undefined."
Signed-off-by: Adam Buchbinder <abuchbinder@xxxxxxxxxx>
It looks good to me.
Reviewed-by: Satoru Takeuchi <takeuchi_satoru@xxxxxxxxxxxxxx>
Thank you both.
The file is taken from kernel/lib/radix-tree.c and has diverged a bit so
it could be missing more bugfixes.
I confirmed the kenel doesn't have such problem.
lib/radix-tree.c (kernel code):
===============================================================================
static __init unsigned long __maxindex(unsigned int height)
{
unsigned int width = height * RADIX_TREE_MAP_SHIFT;
int shift = RADIX_TREE_INDEX_BITS - width;
if (shift < 0)
return ~0UL;
if (shift >= BITS_PER_LONG)
return 0UL;
return ~0UL >> shift;
}
===============================================================================
It's fixed at 430d275a399.
===============================================================================
commit 430d275a399175c7c0673459738979287ec1fd22
Author: Peter Lund <firefly@xxxxxxxx>
Date: Tue Oct 16 23:29:35 2007 -0700
avoid negative (and full-width) shifts in radix-tree.c
...
===============================================================================
Adam, David, how about import this patch from kernel, rather than
writing btrfs-progs's own patch?
P.S.
I consider It's better to regularly sync such utility code with
the newest kernel code for the long term...
Thanks,
Satoru
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