by JMM72 (Posted Wed Jan 04, 2017 4:31 pm)
No, any file with .001 extension is detected as Hayes JTFax format with CCITT Group 3 compression, but only 7zip files cause the crashes here (64 bit XMP). The file must have .001 extension, that's why I detected the crash with the first volume of zplit 7z files. E.g., I rename a 2.3mb PNG with extension .001 and XMP doesn't crash. I compress that file with 7z, rename with extension .001 and it crashes.
I am guessing that JTFax files don't have any header for detection, thus detection only relies on extension. However something inside a 7zip file causes the JTFax decoder to crash, and I see it's something to do with size because small 7z files don't crash.
The files don't need to be huge. Doing some compressions and tests, a file as low as 1679kb causes the crash here. The largest I've tried which doesn't cause the crash is 1482kb. Thus the size which causes the crash is higher than 1482kb but lower than 1679kb. The 1482kb file is detected as an image of 2544 width and 4170 height.
I'm not sure if it's really worth to continue pursuing this bug since it happens under such specific conditions, however one never knows how far a small bug can affect other code. If you are sure the bug is contained within the JTFax decoder and don't want to waste more time, maybe it's better to leave it alone.
Read Main Topic
helmut wrote: I assume that copying and renaming any huge file to .001 can be used for trying to reproduce the problem.
No, any file with .001 extension is detected as Hayes JTFax format with CCITT Group 3 compression, but only 7zip files cause the crashes here (64 bit XMP). The file must have .001 extension, that's why I detected the crash with the first volume of zplit 7z files. E.g., I rename a 2.3mb PNG with extension .001 and XMP doesn't crash. I compress that file with 7z, rename with extension .001 and it crashes.
I am guessing that JTFax files don't have any header for detection, thus detection only relies on extension. However something inside a 7zip file causes the JTFax decoder to crash, and I see it's something to do with size because small 7z files don't crash.
The files don't need to be huge. Doing some compressions and tests, a file as low as 1679kb causes the crash here. The largest I've tried which doesn't cause the crash is 1482kb. Thus the size which causes the crash is higher than 1482kb but lower than 1679kb. The 1482kb file is detected as an image of 2544 width and 4170 height.
I'm not sure if it's really worth to continue pursuing this bug since it happens under such specific conditions, however one never knows how far a small bug can affect other code. If you are sure the bug is contained within the JTFax decoder and don't want to waste more time, maybe it's better to leave it alone.
Read Main Topic