Opened 3 years ago

Closed 3 years ago

Last modified 3 years ago

#119 closed defect (fixed)

Undefined behavior in img.c

Reported by: Matěj Plch Owned by: Olly Betts
Priority: minor Milestone: 1.2.45
Component: Other Version:
Keywords: Cc:


Hi, therion uses img.h and img.c, and when I compile and run therion with Undefined Behavior Sanitizer, this error appears:

UndefinedBehaviorSanitizer: undefined-behavior
../extern/img.c:103:27: runtime error: left shift of 255 by 24 places cannot be represented in type 'int'

Problem is in function get32(), where shifting of signed value by 24 bits interferes with a sign bit. Bitwise operations should be done with unsigned types.

Therion CI job where this error occured:

Change History (5)

comment:1 Changed 3 years ago by Olly Betts

Thanks for reporting.

This also affects Survex itself, but only on big-endian platforms (on little-endian platforms it uses an optimised version of get32() which instead reads 4 bytes from the file in one go) so despite testing Survex with ubsan I hadn't spotted this.

comment:2 Changed 3 years ago by Olly Betts

Milestone: 1.2.45

comment:3 Changed 3 years ago by Olly Betts

Oops, you actually need 227fd9a441d475ad9f79226a8da05a973e10dcd1 as I missed a change (sorry, the power tripped while I was preparing the commit and I lost track of where I'd got to when I turned my computer back on...)

comment:4 Changed 3 years ago by Olly Betts

Resolution: fixed
Status: newclosed

comment:5 Changed 3 years ago by Matěj Plch

Issue is fixed, thank you.

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