https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=230162
Bug ID: 230162
Summary: mprotect(2): error converting size argument in 32-bit
emulation
Product: Base System
Version: CURRENT
Hardware: Any
OS: Any
Status: New
Severity: Affects Only Me
Priority: ---
Component: kern
Assignee: [email protected]
Reporter: [email protected]
The lib/libc/sys/mprotect_test:mprotect_err test fails when run under 32-bit
emulation. Examining the problem with dtrace, it looks like there's a casting
error; the 32-bit syscall's len argument winds up in the high half of
kern_mprotect's size argument. I don't see that behavior when I dtrace msgsnd,
another syscall with a size_t argument.
Here's an example of the problem. Notice how len=0x1 in
syscall:freebsd32_mprotect, but 0x100000000 in fbt:kern_mprotect
$ sudo dtrace -i 'fbt:kernel:kern_mprotect:entry {printf("addr0=%#lx,
size=%#lx", args[1], args[2]);}' -i
'syscall:freebsd32:freebsd32_mprotect:entry {printf("addr=%p len=%#lx",
args[0], args[1]);}' -i 'fbt:kernel:vm_map_protect:entry {printf("size ~=
%#lx", args[2] - args[1]);}'
dtrace: description 'fbt:kernel:kern_mprotect:entry ' matched 1 probe
dtrace: description 'syscall:freebsd32:freebsd32_mprotect:entry ' matched 1
probe
dtrace: description 'fbt:kernel:vm_map_protect:entry ' matched 1 probe
CPU ID FUNCTION:NAME
2 61769 freebsd32_mprotect:entry addr=0 len=0
2 28572 kern_mprotect:entry addr0=0, size=0
2 47917 vm_map_protect:entry size ~= 0
3 61769 freebsd32_mprotect:entry addr=ffffffff len=0x1
3 28572 kern_mprotect:entry addr0=0xfffff000, size=0x100000000
3 47917 vm_map_protect:entry size ~= 0x1000
And in another terminal, in a 32-bit chroot, run
# kyua debug mprotect_test:mprotect_err
mprotect_test:mprotect_err -> failed:
/usr/home/somers/freebsd/base/head/contrib/netbsd-tests/lib/libc/sys/t_mprotect.c:158:
mprotect((char *)-1, 1, PROT_READ) != 0 not met
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