Fix header length handling (again) #2
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added 2 commits
February 14, 2022 10:42
This reverts commit 60dcdaf.
…oblem was that additional fields was not handled at all. Do this handling and check the header length properly. Also, remove an entirely bogus check.
vasi
reviewed
Feb 21, 2022
| @@ -246,6 +246,11 @@ impl Header { | |||
| self.v3.autoclear.set(try!(io.read_u64())); | |||
| self.v3.refcount_order = try!(io.read_u32()); | |||
| self.v3.header_length = try!(io.read_u32()); | |||
| if self.v3.header_length as u64 > io.position() { | |||
| // There are addition fields. | |||
vasi
reviewed
Feb 21, 2022
| self.v3.header_length))); | ||
| } | ||
| if actual_length != HEADER_LENGTH_V3 as u64 { |
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We should get rid of the constant too?
vasi
reviewed
Feb 21, 2022
| @@ -268,16 +273,11 @@ impl Header { | |||
| if self.v3.refcount_order > 6 { | |||
| return Err(Error::FileFormat(format!("bad refcount_order {}", self.v3.refcount_order))); | |||
| } | |||
| if self.v3.header_length as u64 != io.position() { | |||
| if self.v3.header_length as u64 != actual_length { | |||
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I'm not sure if this check is actually useful. We're setting position to header_length, storing that, and then checking if it's what we set it to. Of course it is!
Maybe instead we can check if the length matches the spec? https://github.com/qemu/qemu/blob/master/docs/interop/qcow2.txt#L184-L185
vasi
requested changes
Feb 21, 2022
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Revert the last change to the header length check. Properly skip any additional fields, and make the correct check, also remove an entirely bogus check.This is tested, with both the test image in the tests/ directory, as well as newly created images by qemu-img (6.2) on both MacOS and OpenBSD, according to this vasi/qcow2-fuse#4