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<p>Tags 955440 +patch<br>
Thanks<br>
<br>
The offending code is.<br>
<br>
#if defined(__APPLE__) || defined(__SOLARIS__) ||
defined(__arm__) <br>
// File descriptor passing macros (CMSG_*) seem to
be broken <br>
// on 64-bit MacOS X. This structure works around
the problem. <br>
struct
{ <br>
struct cmsghdr
header; <br>
int
fd; <br>
}
control_data; <br>
#define EXPECTED_CMSG_LEN
sizeof(control_data) <br>
#else
<br>
char
control_data[CMSG_SPACE(sizeof(int))]; <br>
#define EXPECTED_CMSG_LEN
CMSG_LEN(sizeof(int)) <br>
#endif<br>
<br>
And there is another similar block later in the file that likely
suffers from the same issue.<br>
</p>
<p>I took a look at a git blame in upstream git
<a class="moz-txt-link-freetext" href="https://github.com/phusion/passenger/blame/0ef3222e86ede97dff189de1137cca67684d4e2d/src/cxx_supportlib/Utils/IOUtils.cpp#L1128">https://github.com/phusion/passenger/blame/0ef3222e86ede97dff189de1137cca67684d4e2d/src/cxx_supportlib/Utils/IOUtils.cpp#L1128</a>
which leads back to
<a class="moz-txt-link-freetext" href="https://github.com/phusion/passenger/commit/e3885d5c9e7b5403422742f193be0aa5775a84d2">https://github.com/phusion/passenger/commit/e3885d5c9e7b5403422742f193be0aa5775a84d2</a>
but that is just moving the offending code from MessageChannel.h
to IOUtils.cpp so going to the parent commit and blaming again
takes us to
<a class="moz-txt-link-freetext" href="https://github.com/phusion/passenger/commit/312b5e1c65558e17cd30d1b28089078d8f614fbf">https://github.com/phusion/passenger/commit/312b5e1c65558e17cd30d1b28089078d8f614fbf</a>
which added the arm condition to the list of conditionals and is
described as "<span class="blob-code-inner blob-code-marker"
data-code-marker="+">Fixed compilation problems on Linux systems
with ARM CPU</span>".<br>
<br>
My feeling is that the issue that upstream was trying to fix was
an alignment issue. In particular the creation of of a buffer by
using char control_data[CMSG_SPACE(sizeof(int))] means there are
no alignment guarantees on the buffer and if my reading of the
macros is correct then an unaligned buffer will lead to unaligned
accesses. It looks like this bad practice may have originated from
older versions of the manpage, I note that
<a class="moz-txt-link-freetext" href="https://linux.die.net/man/3/cmsg_space">https://linux.die.net/man/3/cmsg_space</a> uses a plain char array
while the manpage in Bullseye uses a union.<br>
<br>
I have written a patch which fixes the alignment issue in the main
codepath and switches arm Linux (and any other non-apple,
non-solaris arm systems) from the alternate codepath to the main
codepath. I have tested that the package builds in raspbian
bullseye-staging with the patch, I have not tested it beyond that.<br>
<br>
I have uploaded the package to raspbian bullseye, a debdiff should
appear soon at <a class="moz-txt-link-freetext" href="https://debdiffs.raspbian.org/main/p/passenger/">https://debdiffs.raspbian.org/main/p/passenger/</a> no
intent to NMU in Debian.<br>
<br>
<br>
</p>
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