[Bug 238642] netmap: fix kernel pointer printing in netmap_generic.c

[bugzilla-noreply at freebsd.org]

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=238642

Aleksandr Fedorov <aleksandr.fedorov at itglobal.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |aleksandr.fedorov at itglobal.
                   |                            |com

--- Comment #5 from Aleksandr Fedorov <aleksandr.fedorov at itglobal.com> ---
It seems something goes wrong. With with changes i saw a panic on CURRENT:

root at current:~ # ifconfig vlan0 create up                                       
root at current:~ # vale-ctl -a vale0:vlan0                                        


Fatal trap 12: page fault while in kernel mode                                  
cpuid = 2; apic id = 02                                                         
fault virtual address   = 0x2a0                                                 
fault code              = supervisor read data, page not present                
instruction pointer     = 0x20:0xffffffff80cb96cf                               
stack pointer           = 0x28:0xfffffe008fa48da0
frame pointer           = 0x28:0xfffffe008fa48da0
code segment            = base 0x0, limit 0xfffff, type 0x1b
                        = DPL 0, pres 1, long 1, def32 0, gran 1
processor eflags        = interrupt enabled, resume, IOPL = 0
current process         = 665 (vale-ctl)
trap number             = 12
panic: page fault                         
cpuid = 2                                 
time = 1562949961                         
KDB: stack backtrace:  
db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe008fa48a60
vpanic() at vpanic+0x19d/frame 0xfffffe008fa48ab0
panic() at panic+0x43/frame 0xfffffe008fa48b10
trap_fatal() at trap_fatal+0x39c/frame 0xfffffe008fa48b70
trap_pfault() at trap_pfault+0x62/frame 0xfffffe008fa48bc0
trap() at trap+0x2b4/frame 0xfffffe008fa48cd0
calltrap() at calltrap+0x8/frame 0xfffffe008fa48cd0
--- trap 0xc, rip = 0xffffffff80cb96cf, rsp = 0xfffffe008fa48da0, rbp =
0xfffffe008fa48da0 ---
strlen() at strlen+0x1f/frame 0xfffffe008fa48da0
kvprintf() at kvprintf+0xf79/frame 0xfffffe008fa48ec0
vprintf() at vprintf+0x81/frame 0xfffffe008fa48f90
printf() at printf+0x43/frame 0xfffffe008fa48ff0
generic_netmap_attach() at generic_netmap_attach+0x309/frame 0xfffffe008fa49040
netmap_get_hw_na() at netmap_get_hw_na+0x81/frame 0xfffffe008fa49070
netmap_get_bdg_na() at netmap_get_bdg_na+0x213/frame 0xfffffe008fa49100
netmap_vale_attach() at netmap_vale_attach+0xe0/frame 0xfffffe008fa49140
netmap_ioctl() at netmap_ioctl+0x8a9/frame 0xfffffe008fa49200
netmap_ioctl_legacy() at netmap_ioctl_legacy+0x4fd/frame 0xfffffe008fa495b0
netmap_ioctl() at netmap_ioctl+0x16b/frame 0xfffffe008fa49670
freebsd_netmap_ioctl() at freebsd_netmap_ioctl+0x88/frame 0xfffffe008fa496b0
devfs_ioctl() at devfs_ioctl+0xca/frame 0xfffffe008fa49700
VOP_IOCTL_APV() at VOP_IOCTL_APV+0x63/frame 0xfffffe008fa49720
vn_ioctl() at vn_ioctl+0x13d/frame 0xfffffe008fa49830
devfs_ioctl_f() at devfs_ioctl_f+0x1f/frame 0xfffffe008fa49850
kern_ioctl() at kern_ioctl+0x28a/frame 0xfffffe008fa498c0
sys_ioctl() at sys_ioctl+0x15d/frame 0xfffffe008fa49990
amd64_syscall() at amd64_syscall+0x276/frame 0xfffffe008fa49ab0
fast_syscall_common() at fast_syscall_common+0x101/frame 0xfffffe008fa49ab0
--- syscall (54, FreeBSD ELF64, sys_ioctl), rip = 0x80041631a, rsp =
0x7fffffffeab8, rbp = 0x7fffffffeb50 ---
KDB: enter: panic
[ thread pid 665 tid 100131 ]
Stopped at      kdb_enter+0x3b: movq    $0,kdb_why
db> 

This happens due the fact that gna->prev equal zero.

For example old output without this patch:
root at current:~ # vale-ctl -a vale0:vlan0
792.670615 [1130] generic_netmap_attach     Emulated adapter for vlan0 created
(prev was 0)
                                                                               
   ^^^^^^^!!!!!
I don't know why, but this if evaluated as false:

1121     if (NM_NA_VALID(ifp)) {
1122         gna->prev = NA(ifp); /* save old na */
1123         netmap_adapter_get(gna->prev);
1124     }

And then:

1129     nm_prinf("Emulated adapter for %s created (prev was %s)", na->name,
gna->prev->name);
                                                                               
  ^^^^!!!!
Null pointer dereference.

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