In this output the second report, for sys_extattr_get_file(data) is unexpected:
Syscall param extattr_get_file(nbytes) contains uninitialised byte(s)
at 0x........: extattr_get_file (in /...libc...)
by 0x........: main (extattr.c:35)
Syscall param sys_extattr_get_file(data) points to unaddressable byte(s)
at 0x........: extattr_get_file (in /...libc...)
by 0x........: main (extattr.c:35)
Address 0x........ is not stack'd, malloc'd or (recently) free'd
In this output the second report, for sys_extattr_get_file(data) is unexpected:
from extattr.c:35:
The implementation in syswrap-freebsd.c which is reporting this is:
In this case, the uninitialized ARG5 happened to be 0xFBBFEBC8, so yes, accessing that much of ARG4 would run into unaddressable bytes.