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linux/kernel
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Gianluca Borello a60dd35d2e bpf: change bpf_perf_event_output arg5 type to ARG_CONST_SIZE_OR_ZERO 
Commit 9fd29c08e5 ("bpf: improve verifier ARG_CONST_SIZE_OR_ZERO
semantics") relaxed the treatment of ARG_CONST_SIZE_OR_ZERO due to the way
the compiler generates optimized BPF code when checking boundaries of an
argument from C code. A typical example of this optimized code can be
generated using the bpf_perf_event_output helper when operating on variable
memory:

/* len is a generic scalar */
if (len > 0 && len <= 0x7fff)
        bpf_perf_event_output(ctx, &perf_map, 0, buf, len);

110: (79) r5 = *(u64 *)(r10 -40)
111: (bf) r1 = r5
112: (07) r1 += -1
113: (25) if r1 > 0x7ffe goto pc+6
114: (bf) r1 = r6
115: (18) r2 = 0xffff94e5f166c200
117: (b7) r3 = 0
118: (bf) r4 = r7
119: (85) call bpf_perf_event_output#25
R5 min value is negative, either use unsigned or 'var &= const'

With this code, the verifier loses track of the variable.

Replacing arg5 with ARG_CONST_SIZE_OR_ZERO is thus desirable since it
avoids this quite common case which leads to usability issues, and the
compiler generates code that the verifier can more easily test:

if (len <= 0x7fff)
        bpf_perf_event_output(ctx, &perf_map, 0, buf, len);

or

bpf_perf_event_output(ctx, &perf_map, 0, buf, len & 0x7fff);

No changes to the bpf_perf_event_output helper are necessary since it can
handle a case where size is 0, and an empty frame is pushed.

Reported-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Gianluca Borello <g.borello@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2017-11-22 21:40:54 +01:00
..
bpf bpf: introduce ARG_PTR_TO_MEM_OR_NULL 2017-11-22 21:40:54 +01:00
cgroup Merge branch 'for-4.15' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2017-11-15 14:29:44 -08:00
configs
debug
events Tracing updates for 4.15: 2017-11-17 14:58:01 -08:00
gcov License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
irq arm64 updates for 4.15 2017-11-15 10:56:56 -08:00
livepatch Merge branch 'for-linus' of ssh://gitolite.kernel.org/pub/scm/linux/kernel/git/jikos/livepatching 2017-11-15 10:21:58 -08:00
locking kmemcheck: remove annotations 2017-11-15 18:21:04 -08:00
power mm: remove __GFP_COLD 2017-11-15 18:21:06 -08:00
printk Tracing updates for 4.15: 2017-11-17 14:58:01 -08:00
rcu Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-11-13 17:56:58 -08:00
sched Merge branch 'misc.compat' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-11-17 11:54:55 -08:00
time Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-11-13 17:56:58 -08:00
trace bpf: change bpf_perf_event_output arg5 type to ARG_CONST_SIZE_OR_ZERO 2017-11-22 21:40:54 +01:00
.gitignore
acct.c Merge branch 'linus' into locking/core, to resolve conflicts 2017-11-07 10:32:44 +01:00
async.c
audit_fsnotify.c
audit_tree.c Merge branch 'fsnotify' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs 2017-11-14 14:08:20 -08:00
audit_watch.c
audit.c Audit: remove unused audit_log_secctx function 2017-11-10 16:08:47 -05:00
audit.h audit/stable-4.15 PR 20171113 2017-11-15 13:28:48 -08:00
auditfilter.c audit: filter PATH records keyed on filesystem magic 2017-11-10 16:08:56 -05:00
auditsc.c audit/stable-4.15 PR 20171113 2017-11-15 13:28:48 -08:00
backtracetest.c
bounds.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
capability.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
compat.c
configs.c
context_tracking.c
cpu_pm.c
cpu.c cpu/hotplug: Reset node state after operation 2017-10-21 16:11:30 +02:00
crash_core.c kdump: print a message in case parse_crashkernel_mem resulted in zero bytes 2017-11-17 16:10:03 -08:00
crash_dump.c
cred.c
delayacct.c
dma.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
elfcore.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
exec_domain.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
exit.c locking/atomics: COCCINELLE/treewide: Convert trivial ACCESS_ONCE() patterns to READ_ONCE()/WRITE_ONCE() 2017-10-25 11:01:08 +02:00
extable.c kprobes, x86/alternatives: Use text_mutex to protect smp_alt_modules 2017-11-07 12:20:09 +01:00
fork.c pid: remove pidhash 2017-11-17 16:10:04 -08:00
freezer.c
futex_compat.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
futex.c Merge branch 'linus' into core/urgent, to pick up dependent commits 2017-11-04 08:53:04 +01:00
groups.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
hung_task.c
irq_work.c Merge branch 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-11-13 17:33:11 -08:00
jump_label.c locking/static_keys: Improve uninitialized key warning 2017-10-19 07:49:14 +02:00
kallsyms.c Tracing updates for 4.15: 2017-11-17 14:58:01 -08:00
kcmp.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt
kcov.c kcov: support comparison operands collection 2017-11-17 16:10:04 -08:00
kexec_core.c
kexec_file.c resource: Provide resource struct in resource walk callback 2017-11-07 15:35:57 +01:00
kexec_internal.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
kexec.c
kmod.c
kprobes.c kprobes: Disable the jprobes APIs 2017-10-20 11:02:29 +02:00
ksysfs.c
kthread.c Merge branch 'for-4.15/block' of git://git.kernel.dk/linux-block 2017-11-14 15:32:19 -08:00
latencytop.c
Makefile License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
memremap.c memremap: add scheduling point to devm_memremap_pages 2017-10-03 17:54:25 -07:00
module_signing.c
module-internal.h
module.c Tracing updates for 4.15: 2017-11-17 14:58:01 -08:00
notifier.c
nsproxy.c
padata.c padata: ensure padata_do_serial() runs on the correct CPU 2017-10-07 12:10:32 +08:00
panic.c kernel/panic.c: add TAINT_AUX 2017-11-17 16:10:04 -08:00
params.c kernel/params.c: improve STANDARD_PARAM_DEF readability 2017-10-03 17:54:26 -07:00
pid_namespace.c pid: remove pidhash 2017-11-17 16:10:04 -08:00
pid.c pid: remove pidhash 2017-11-17 16:10:04 -08:00
profile.c
ptrace.c
range.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
reboot.c kernel/reboot.c: add devm_register_reboot_notifier() 2017-11-17 16:10:04 -08:00
relay.c
resource.c x86/mm, resource: Use PAGE_KERNEL protection for ioremap of memory pages 2017-11-07 15:35:58 +01:00
seccomp.c Merge branch 'linus' into locking/core, to resolve conflicts 2017-11-07 10:32:44 +01:00
signal.c Merge branch 'akpm' (patches from Andrew) 2017-11-17 16:56:17 -08:00
smp.c smp/core: Use lockdep to assert IRQs are disabled/enabled 2017-11-08 11:13:50 +01:00
smpboot.c watchdog/core, powerpc: Lock cpus across reconfiguration 2017-10-04 10:53:54 +02:00
smpboot.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
softirq.c kmemcheck: rip it out 2017-11-15 18:21:05 -08:00
stacktrace.c
stop_machine.c
sys_ni.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
sys.c arm64 updates for 4.15 2017-11-15 10:56:56 -08:00
sysctl_binary.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
sysctl.c kernel/sysctl.c: code cleanups 2017-11-17 16:10:03 -08:00
task_work.c Merge branch 'linus' into locking/core, to resolve conflicts 2017-11-07 10:32:44 +01:00
taskstats.c
test_kprobes.c kprobes: Disable the jprobes test code 2017-10-20 11:02:54 +02:00
torture.c
tracepoint.c
tsacct.c
ucount.c
uid16.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
umh.c kernel/umh.c: optimize 'proc_cap_handler()' 2017-11-17 16:10:01 -08:00
up.c
user_namespace.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2017-11-16 12:20:15 -08:00
user-return-notifier.c
user.c userns: use union in {g,u}idmap struct 2017-10-31 17:22:58 -05:00
utsname_sysctl.c
utsname.c
watchdog_hld.c Merge branch 'linus' into core/urgent, to pick up dependent commits 2017-11-04 08:53:04 +01:00
watchdog.c Merge branch 'linus' into sched/core, to pick up fixes 2017-11-08 10:17:15 +01:00
workqueue_internal.h Merge branch 'for-4.14-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq 2017-11-06 12:26:49 -08:00
workqueue.c Merge branch 'for-4.15' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq 2017-11-15 14:15:21 -08:00