Bug 215504

Summary: limits -s 0 limits causes limits process to segfault
Product: Base System Reporter: Enji Cooper <ngie>
Component: binAssignee: freebsd-bugs (Nobody) <bugs>
Status: New ---    
Severity: Affects Only Me CC: markj
Priority: ---    
Version: CURRENT   
Hardware: Any   
OS: Any   

Description Enji Cooper freebsd_committer 2016-12-23 05:29:30 UTC
# limits -s 0 limits
Segmentation fault (core dumped)
# whoami
root
# gdb limits limits.core
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Reading symbols from limits...Reading symbols from /usr/src/svn/usr.bin/limits/limits.debug...done.
done.
[New LWP 100106]
Core was generated by `limits -s 0 limits'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x0000000800ab40a0 in setrlimit () from /lib/libc.so.7
(gdb) bt
#0  0x0000000800ab40a0 in setrlimit () from /lib/libc.so.7
Backtrace stopped: Cannot access memory at address 0x7fffffffe8e8
Comment 1 Mark Johnston freebsd_committer 2016-12-24 23:16:53 UTC
Presumably this is because you asked limits to execute with a stack size of 0? Looking at kern_proc_setrlimit(), a request to decrease the current stack limit will cause the kernel to render inaccessible any pages beyond the new limit, so with a new size of 0 we'll crash upon returning from setrlimit(). (It also looks as though kern_proc_setrlimit() assumes that stacks grow down.)