https://bugs.kde.org/show_bug.cgi?id=498143
Bug ID: 498143
Summary: False positive on EVIOCGRAB ioctl.
Classification: Developer tools
Product: valgrind
Version: 3.23.0
Platform: Debian unstable
OS: Linux
Status: REPORTED
Severity: minor
Priority: NOR
Component: general
Assignee: jsew...@acm.org
Reporter: me@tali.network
Target Milestone: ---
The EVIOCGRAB ioctl takes as argument just one parameter and tests whether it's
truthy: It does *not* dereference the argument. Valgrind, however, doesn't
agree, and logs a warning like the following when one calls ioctl(fd,
EVIOCGRAB, 1):
```
==6155== Thread 3:
==6155== Syscall param ioctl(generic) points to unaddressable byte(s)
==6155== at 0x4A9723B: ioctl (ioctl.c:36)
...
==6155== Address 0x1 is not stack'd, malloc'd or (recently) free'd
```
STEPS TO REPRODUCE
1. Run valgrind on a program that calls ioctl(some_fd, EVIOCGRAB, 1); (or any
other truthy value)
OBSERVED RESULT
False positive warning.
EXPECTED RESULT
No warning; this is safe code.
SOFTWARE/OS VERSIONS
This is on Debian Sid, but I've reproduced it on Fedora as well. This affects
(at least) Linuxes 6.12.4 and 6.12.6. Valgrind v3.2.0 and 3.24.0.
ADDITIONAL INFORMATION
Let me know if there's any other info I can provide. Thanks :)
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