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Daniel Borkmann e929e019f4 bpf: Fix truncation handling for mod32 dst reg wrt zero 
commit 9b00f1b78809309163dda2d044d9e94a3c0248a3 upstream.

Recently noticed that when mod32 with a known src reg of 0 is performed,
then the dst register is 32-bit truncated in verifier:

  0: R1=ctx(id=0,off=0,imm=0) R10=fp0
  0: (b7) r0 = 0
  1: R0_w=inv0 R1=ctx(id=0,off=0,imm=0) R10=fp0
  1: (b7) r1 = -1
  2: R0_w=inv0 R1_w=inv-1 R10=fp0
  2: (b4) w2 = -1
  3: R0_w=inv0 R1_w=inv-1 R2_w=inv4294967295 R10=fp0
  3: (9c) w1 %= w0
  4: R0_w=inv0 R1_w=inv(id=0,umax_value=4294967295,var_off=(0x0; 0xffffffff)) R2_w=inv4294967295 R10=fp0
  4: (b7) r0 = 1
  5: R0_w=inv1 R1_w=inv(id=0,umax_value=4294967295,var_off=(0x0; 0xffffffff)) R2_w=inv4294967295 R10=fp0
  5: (1d) if r1 == r2 goto pc+1
   R0_w=inv1 R1_w=inv(id=0,umax_value=4294967295,var_off=(0x0; 0xffffffff)) R2_w=inv4294967295 R10=fp0
  6: R0_w=inv1 R1_w=inv(id=0,umax_value=4294967295,var_off=(0x0; 0xffffffff)) R2_w=inv4294967295 R10=fp0
  6: (b7) r0 = 2
  7: R0_w=inv2 R1_w=inv(id=0,umax_value=4294967295,var_off=(0x0; 0xffffffff)) R2_w=inv4294967295 R10=fp0
  7: (95) exit
  7: R0=inv1 R1=inv(id=0,umin_value=4294967295,umax_value=4294967295,var_off=(0x0; 0xffffffff)) R2=inv4294967295 R10=fp0
  7: (95) exit

However, as a runtime result, we get 2 instead of 1, meaning the dst
register does not contain (u32)-1 in this case. The reason is fairly
straight forward given the 0 test leaves the dst register as-is:

  # ./bpftool p d x i 23
   0: (b7) r0 = 0
   1: (b7) r1 = -1
   2: (b4) w2 = -1
   3: (16) if w0 == 0x0 goto pc+1
   4: (9c) w1 %= w0
   5: (b7) r0 = 1
   6: (1d) if r1 == r2 goto pc+1
   7: (b7) r0 = 2
   8: (95) exit

This was originally not an issue given the dst register was marked as
completely unknown (aka 64 bit unknown). However, after 468f6eafa6c4
("bpf: fix 32-bit ALU op verification") the verifier casts the register
output to 32 bit, and hence it becomes 32 bit unknown. Note that for
the case where the src register is unknown, the dst register is marked
64 bit unknown. After the fix, the register is truncated by the runtime
and the test passes:

  # ./bpftool p d x i 23
   0: (b7) r0 = 0
   1: (b7) r1 = -1
   2: (b4) w2 = -1
   3: (16) if w0 == 0x0 goto pc+2
   4: (9c) w1 %= w0
   5: (05) goto pc+1
   6: (bc) w1 = w1
   7: (b7) r0 = 1
   8: (1d) if r1 == r2 goto pc+1
   9: (b7) r0 = 2
  10: (95) exit

Semantics also match with {R,W}x mod{64,32} 0 -> {R,W}x. Invalid div
has always been {R,W}x div{64,32} 0 -> 0. Rewrites are as follows:

  mod32:                            mod64:

  (16) if w0 == 0x0 goto pc+2       (15) if r0 == 0x0 goto pc+1
  (9c) w1 %= w0                     (9f) r1 %= r0
  (05) goto pc+1
  (bc) w1 = w1

Fixes: 468f6eafa6c4 ("bpf: fix 32-bit ALU op verification")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 		2021-04-12 12:52:08 +08:00
..
bpf bpf: Fix truncation handling for mod32 dst reg wrt zero 2021-04-12 12:52:08 +08:00
cgroup cgroup: fix psi monitor for root cgroup 2021-04-12 12:52:01 +08:00
configs Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
debug kgdb: Make "kgdbcon" work properly with "kgdb_earlycon" 2021-03-16 16:39:45 +08:00
dma swiotlb: fix "x86: Don't panic if can not alloc buffer for swiotlb" 2021-03-16 16:40:57 +08:00
events exec: Transform exec_update_mutex into a rw_semaphore 2021-04-12 12:51:05 +08:00
gcov gcov: add support for GCC 10.1 2021-03-16 16:36:10 +08:00
irq genirq/msi: Activate Multi-MSI early when MSI_FLAG_ACTIVATE_EARLY is set 2021-04-12 12:51:55 +08:00
livepatch Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
locking rtmutex: Remove unused argument from rt_mutex_proxy_unlock() 2021-04-12 12:51:41 +08:00
power PM: hibernate: flush swap writer after marking 2021-04-12 12:51:43 +08:00
printk printk: handle blank console arguments passed in. 2021-03-16 16:37:21 +08:00
rcu arm64: smp: Tell RCU about CPUs that fail to come online 2021-03-16 16:41:11 +08:00
sched sched/fair: Check for idle core in wake_affine 2021-03-18 06:25:56 +00:00
time tick/sched: Remove bogus boot "safety" check 2021-03-16 16:43:56 +08:00
tkernel Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
trace tracing: Check length before giving out the filter buffer 2021-04-12 12:52:01 +08:00
.gitignore Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
Kconfig.freezer Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
Kconfig.hz Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
Kconfig.locks Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
Kconfig.preempt Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
Makefile elfcore: fix building with clang 2021-04-12 12:51:29 +08:00
acct.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
async.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
audit.c audit: fix a net reference leak in audit_list_rules_send() 2021-03-16 16:29:25 +08:00
audit.h audit: fix a net reference leak in audit_list_rules_send() 2021-03-16 16:29:25 +08:00
audit_fsnotify.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
audit_tree.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
audit_watch.c audit: CONFIG_CHANGE don't log internal bookkeeping as an event 2021-03-16 16:36:51 +08:00
auditfilter.c audit: fix a net reference leak in audit_list_rules_send() 2021-03-16 16:29:25 +08:00
auditsc.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
backtracetest.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
bounds.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
capability.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
compat.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
configs.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
context_tracking.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
cpu.c kernel/cpu: add arch override for clear_tasks_mm_cpumask() mm handling 2021-03-16 16:42:28 +08:00
cpu_pm.c kernel/cpu_pm: Fix uninitted local in cpu_pm 2021-03-16 16:29:48 +08:00
crash_core.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
crash_dump.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
cred.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
delayacct.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
dma.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
exec_domain.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
exit.c don't dump the threads that had been already exiting when zapped. 2021-03-16 16:40:57 +08:00
extable.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
fail_function.c fail_function: Remove a redundant mutex unlock 2021-03-16 16:41:23 +08:00
fork.c exec: Transform exec_update_mutex into a rw_semaphore 2021-04-12 12:51:05 +08:00
freezer.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
futex.c futex: Handle faults correctly for PI futexes 2021-04-12 12:51:41 +08:00
gen_kheaders.sh kbuild: add variables for compression tools 2021-03-16 16:35:19 +08:00
groups.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
hung_task.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
iomem.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
irq_work.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
jump_label.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
kallsyms.c kallsyms: Refactor kallsyms_show_value() to take cred 2021-03-16 16:31:37 +08:00
kcmp.c exec: Transform exec_update_mutex into a rw_semaphore 2021-04-12 12:51:05 +08:00
kcov.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
kexec.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
kexec_core.c kernel: kexec: remove the lock operation of system_transition_mutex 2021-04-12 12:51:43 +08:00
kexec_elf.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
kexec_file.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
kexec_internal.h Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
kheaders.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
kmod.c kmod: make request_module() return an error when autoloading is disabled 2021-03-16 16:26:15 +08:00
kprobes.c tracing/kprobe: Fix to support kretprobe events on unloaded modules 2021-04-12 12:51:58 +08:00
ksysfs.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
kthread.c kthread: Extract KTHREAD_IS_PER_CPU 2021-04-12 12:51:51 +08:00
latencytop.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
module-internal.h Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
module.c module: delay kobject uevent until after module init call 2021-03-16 16:43:55 +08:00
module_signature.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
module_signing.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
notifier.c kernel/notifier.c: intercept duplicate registrations to avoid infinite loops 2021-03-16 16:36:43 +08:00
nsproxy.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
padata.c padata: add separate cpuhp node for CPUHP_PADATA_DEAD 2021-03-16 16:28:57 +08:00
panic.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
params.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
pid.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
pid_namespace.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
profile.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
ptrace.c ptrace: Set PF_SUPERPRIV when checking capability 2021-03-16 16:41:32 +08:00
range.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
reboot.c reboot: fix overflow parsing reboot cpu number 2021-03-16 16:40:55 +08:00
relay.c kernel/relay.c: fix memleak on destroy relay channel 2021-03-16 16:34:28 +08:00
resource.c /dev/mem: Revoke mappings when a driver claims the region 2021-03-16 16:30:25 +08:00
rseq.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
seccomp.c seccomp: Set PF_SUPERPRIV when checking capability 2021-03-16 16:41:32 +08:00
signal.c ptrace: fix task_join_group_stop() for the case when current is traced 2021-03-16 16:40:18 +08:00
smp.c smp: introduce a new interface smp_call_function_many_async 2021-03-18 06:25:56 +00:00
smpboot.c kthread: Extract KTHREAD_IS_PER_CPU 2021-04-12 12:51:51 +08:00
smpboot.h Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
softirq.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
stackleak.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
stacktrace.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
stop_machine.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
sys.c kernel/sys.c: avoid copying possible padding bytes in copy_to_user 2021-03-16 16:36:43 +08:00
sys_ni.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
sysctl-test.c kernel/sysctl-test: Add null pointer test for sysctl.c:proc_dointvec() 2021-03-16 16:36:31 +08:00
sysctl.c net: rps using pvipi 2021-03-19 08:24:58 +00:00
sysctl_binary.c net: change TCP_TIMEWAIT_LEN on runtime 2021-03-16 16:43:58 +08:00
task_work.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
taskstats.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
test_kprobes.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
torture.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
tracepoint.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
tsacct.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
ucount.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
uid16.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
uid16.h Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
umh.c usermodehelper: reset umask to default before executing user process 2021-03-16 16:37:54 +08:00
up.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
user-return-notifier.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
user.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
user_namespace.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
utsname.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
utsname_sysctl.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
watchdog.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
watchdog_hld.c Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
workqueue.c workqueue: Restrict affinity change to rescuer 2021-04-12 12:51:51 +08:00
workqueue_internal.h Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00