Hello Jay
Good day to you. I looked into the changes.
Here are my views-
. As per the code changes in the lines mentioned below, every "Throwable"
(other than the 4 exceptions listed in the first catch block) is considered-
"BufferOverflow/OOM". This is incorrect.
. Say for example, a future change to code within readImage method
resulted in a NullPointerException, this would get incorrectly reported as-
BufferOverflow/ OOM as per the changes.
. Secondly, throwing one IIOException with a combined message will confuse
the programmer- Was it OOM ? or was it BufferOverflow that caused the reader to
exit ?
. If the intent is to process and throw IIOException with meaningful
message, I believe, we should handle them separately and throw one IIOException
for each with a suitable message.
1675 } catch (IOException |
1676 IndexOutOfBoundsException |
1677 IllegalStateException |
1678 IllegalArgumentException e)
1679 {
1680 throw e;
1681 } catch (Throwable e) {
1682 throw new IIOException("BufferOverflow/OOM while reading"
1683 + " the image");
1684 }
Thanks
Have a good day
Prahalad
----- Original Message -----
From: Jayathirth D V
Sent: Monday, November 13, 2017 2:53 PM
To: 2d-dev
Subject: [OpenJDK 2D-Dev] [10] RFR JDK-8190332: PngReader throws
NegativeArraySizeException/OOM error when IHDR width is very large
Hello All,
Please review the following fix in JDK10 :
Bug : https://bugs.openjdk.java.net/browse/JDK-8190332
Webrev : http://cr.openjdk.java.net/~jdv/8190332/webrev.00/
Issue :
Two types of issues are fixed under the same solution, so JDK-8190511 is
closed as duplicate of this issue.
1) PNGImageReader throws OOM error when IHDR width equals/or greater
than VM's array size limit.
2) PNGImageReader throws NegativeArraySizeException when IHDR width
value is very high.
Root cause :
1) VM doesn't allow creation of array with Size >= ((2 to the power of 31) - 2)
so we throw OOM error.
2) We use width from IHDR to calculate needed "bytesPerRow" value as
"(inputBands*passWidth*bitDepth + 7)/8". When IHDR width is very high we
overflow the integer size of bytesPerRow and when we try to create array using
bytesPerRow it throws NegativeArraySizeException.
Solution :
According to PNG spec maximum value that can be stored in IHDR
width/height is (2 to the power of 31). We can't support PNG images with so
large height/width, because based on other parameters like inputsBands,
bitDepth we will definitely overflow than the maximum buffer value of
VM. Also PNG is not a preferred format for such kind of large images.
Instead of catching these OOMError/NegativeArraySizeException
at many different levels in PNGImageReader we can catch Throwable at higher
level and convert OOMError/ NegativeArraySizeException into IIOException.
Thanks,
Jay
