On 2012-09-16, at 12:46 PM, Li Xi wrote:
> I have a question about function ll_listxattr(). According to the standard,
> listxattr(2) should return -1if the size of the list buffer is too small to
> hold the result. However ll_listxattr() will return a value bigger than
> buffer size in some cases.
>
> Let's assume listxattr(2) returns SIZE when it is called with a large enough
> list buffer. If it's called with a list buffer whose size is smaller than
> SIZE but bigger than SIZE-12, then listxattr(2) will return SIZE too. I got
> the result on Lustre-2.2. I believe it is not a correct result.
>
> The following codes in ll_listxattr() causes this problem:
>
> if (buffer && (rc + total_len) <= size) {
> buffer += rc;
> memcpy(buffer,XATTR_LUSTRE_PREFIX, prefix_len);
> memcpy(buffer+prefix_len, "lov", name_len);
> buffer[prefix_len + name_len] = '\0';
> }
> rc2 = total_len;
>
> I think when '(rc + total_len) <= size' is false and the buffer is not NULL,
> the return valuse should be set to -1.
>
> Is that a problem or a feature?
Definitely looks like a bug. Could you please file a ticket at
http://bugs.whamcloud.com/ and submit a patch for this? Please see the
http://wiki.whamcloud.com/display/PUB/Submitting+Changes page for details.
Cheers, Andreas
--
Andreas Dilger Whamcloud, Inc.
Principal Lustre Engineer http://www.whamcloud.com/
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