Hi Goetz,
Quick follow up on a couple of things ...
On 3/11/2015 7:33 PM, Lindenmaier, Goetz wrote:
Hi David,
Sorry, lots of folks very busy at the moment as we try to get features
finalized before the deadline.
thanks for looking at this! I know the Dec. 10 deadline, but I guess that also
holds for us ... at least J1 is over now. (Unfortunately we could not attend
this year.)
Me neither :)
ps_core.c:
Pread not necessarily terminates interp_name which is printed thereafter.
Increase buffer size by 1 and add '\0'.
Given:
#define BUF_SIZE (PATH_MAX + NAME_MAX + 1)
isn't it impossible to encounter that problem?
As I understand, pread does not null-terminate what it read. So the
null must come from the file. This protects against a corrupted file.
So are you saying the nul is not present in the file? I'm not familiar
with the ELF format.
stubRoutines_x86.cpp:
Cast to proper type. This way, left and right of '&' have the same type.
I think you could just have changed the uint64_t to uint32_t as applied
to the shift rather than casting the 1 to uint_32t. End result is the
same though.
What you propose did not work. It was my first fix, too.
Hmm okay. The result of the shift must be an unsigned type and the
constant 1 is signed, so needs the cast (or use the unsigned constant
form - 1ud? )
attachListener_linux.cpp:
Read does not terminate buf. Size for '\0' is already considered.
Looks a little odd being done on each iteration, but okay I guess.
I'll try to move it out of the loop. Better: I'll check whether the
scan groks it if I move it out of the loop :)
os_linux.cpp:
Array sigflags[] has size MAXSIGNUM==32. _NSIG is bigger than
MAXSIGNUM (_NSIG == 65 on my machine).
sig is checked to be smaller than _NSIG. Later, in set_our_sigflags(),
sig is used to access sigflags[MAXSIGNUM] which can overflow the array.
Should we also increase MAXSIGNUM?
Need to let the SR folk comment here as something definitely seems
wrong, but I'm not 100% sure the what the correct answer is. If
_JAVA_SR_SIGNUM is too big it should be validated somewhere and an error
or warning reported.
I'm also not sure how to best handle this. Might even require a fix
exceeding this change. But I think this is the best finding.
codeBuffer.cpp:
New_capacity is not initialized. Figure_expanded_capacities() handles this
correctly, but initializing this is cheap and safe.
Hmmm ... I hate redundancy - this is pure wasted cycles. If we had to do
it would memset not be better? Or would the code-checker not realize
what memset was doing?
I guess it would work with memset, too. But I thought the 3-deep loop
will be unrolled completely so that only three stores remain.
I tend not to try and imagine what the compiler may or may not do. Happy
to take other opinions. Though again I'd prefer if the checker could be
shown that there is no missing initialization.
dict.cpp:
If j-- is executed for j==0, the loop aborts because j is unsigned (0-- >= b-
_cnt).
Instead, only do j++ if necessary.
Not at all obvious to me that it is possible to do j-- when j==0, but
the change seems reasonable.
Yes, the scan does not understand there is j++ right after j-- because
of the loop iteration. I saw it complaining about this pattern several times.
Lots of spacing changes in that code make it hard to see the real changes.
Before, I was asked to fix indentation issues in a function I touch.
Does that only hold for compiler files?
Yes/no/maybe :) Fixing up bad formatting when you are touching an area
can be convenient, however it can also obscure the real changes, so it
depends on the ratio of functional changes to format changes.
145 // SAPJVM GL j-- can underflow, which will cause the loop to abort.
Seems unnecessary with the code change as noone will understand what j--
you are referring to.
Didn't mean to leave this in here. Removed.
150 nb->_keyvals[nbcnt + nbcnt ] = key;
151 nb->_keyvals[nbcnt + nbcnt + 1] = b->_keyvals[j+j+1];
hotspot-style doesn't align array index expressions like that. Ditto
154/155.
Fixed.
generateOopMap.cpp:
Idx is read from String. This is only called with constant strings, so compare
should be folded away by optimizing compilers if inlined.
Not a fan of adding conditions that should never be false (hence the
assert) and relying on the compiler to elide them.
OK, removed.
deoptimization.cpp:
If buflen == 0, buf[-1] is accessed.
Okay - but an assert(buflen>0) would be better I think as we should
never be calling with a zero-length buffer.
Ok, I added the assert. As this isn't critical code, I would like to leave the
check in there, still.
task.cpp:
Fatal can return if -XX:SuppressErrorAt is used. Just don't access the
array in this case.
Okay. I would not be surprised if we have a lot of potential errors if a
fatal/guarantee failure is suppressed.
attachListener.hpp:
Do strncpy to not overflow buffer. Don't write more chars than before.
Again we have the assert to catch an error in the caller using an
invalid name.
Hmm, the command comes from outside of the VM. It's not checked
very thoroughly, see, e.g., attachListener_windows.cpp:194. Arg0 is
checked twice, arg1 and arg2 are not checked at all.
The libattach code is still part of our codebase so should be doing the
right things. The linux and solaris code seems to be doing the expected
name length check. On Windows the name is set using cmd, which is also
subject to a length check:
if (strlen(cmd) > AttachOperation::name_length_max) return
ATTACH_ERROR_ILLEGALARG;
I add fixes for attachListener_windows.cpp to this change.
heapDumper.cpp:
strncpy does not null terminate.
1973 if (total_length >= sizeof(base_path)) {
total_length already adds +1 for the nul character so the == case is
fine AFAICS.
strncpy wont nul-terminate if the string exceeds the buffer size. But we
have already established that total_length <= sizeof(base_path), and
total_path includes space for a bunch of stuff other than HeapDumpPath,
so the strncpy of HeapDumpPath has to copy the nul character.
Ok, removed.
> src/share/vm/services/memoryService.cpp
Ok.
> src/share/vm/utilities/xmlstream.cpp
Ok - I'm more concerned about the "magic" 10 in that piece of code.
I assume the 10 is the space needed for the "_done" plus some waste ...
I'll do another run of the scan. That takes a day. I'll post a new webrev
after
that.
Thanks,
David
Thank again for this thorough review,
Goetz
Some of these, as the issue in codeBuffer.cpp, are actually handled correctly.
Nevertheless this is not that obvious so that somebody changing the code
Could oversee he has to add the initialization.
Not an argument I buy en-masse as it leads to a lot of redundancy
through the code paths. Plus these tools that are being run should show
if a code changes requires initialization that is not present.
Thanks,
David
Some of these fixes are part of SAP JVM for a long time. This change has
been tested with our nightly build of openJDK.
Best regards,
Goetz,.
