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linux/kernel
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Daniel Borkmann 801c6058d1 bpf: Fix leakage of uninitialized bpf stack under speculation 
The current implemented mechanisms to mitigate data disclosure under
speculation mainly address stack and map value oob access from the
speculative domain. However, Piotr discovered that uninitialized BPF
stack is not protected yet, and thus old data from the kernel stack,
potentially including addresses of kernel structures, could still be
extracted from that 512 bytes large window. The BPF stack is special
compared to map values since it's not zero initialized for every
program invocation, whereas map values /are/ zero initialized upon
their initial allocation and thus cannot leak any prior data in either
domain. In the non-speculative domain, the verifier ensures that every
stack slot read must have a prior stack slot write by the BPF program
to avoid such data leaking issue.

However, this is not enough: for example, when the pointer arithmetic
operation moves the stack pointer from the last valid stack offset to
the first valid offset, the sanitation logic allows for any intermediate
offsets during speculative execution, which could then be used to
extract any restricted stack content via side-channel.

Given for unprivileged stack pointer arithmetic the use of unknown
but bounded scalars is generally forbidden, we can simply turn the
register-based arithmetic operation into an immediate-based arithmetic
operation without the need for masking. This also gives the benefit
of reducing the needed instructions for the operation. Given after
the work in 7fedb63a83 ("bpf: Tighten speculative pointer arithmetic
mask"), the aux->alu_limit already holds the final immediate value for
the offset register with the known scalar. Thus, a simple mov of the
immediate to AX register with using AX as the source for the original
instruction is sufficient and possible now in this case.

Reported-by: Piotr Krysiuk <piotras@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Piotr Krysiuk <piotras@gmail.com>
Reviewed-by: Piotr Krysiuk <piotras@gmail.com>
Reviewed-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
2021-05-03 11:56:23 +02:00
..
bpf bpf: Fix leakage of uninitialized bpf stack under speculation 2021-05-03 11:56:23 +02:00
cgroup cgroup: use tsk->in_iowait instead of delayacct_is_task_waiting_on_io() 2021-04-16 16:49:37 -04:00
configs staging: ION: remove some references to CONFIG_ION 2021-01-06 17:39:38 +01:00
debug printk changes for 5.13 2021-04-27 18:09:44 -07:00
dma Merge branch 'stable/for-linus-5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/swiotlb 2021-02-26 13:59:32 -08:00
entry A trivial cleanup of typo fixes. 2021-04-26 09:41:15 -07:00
events perf: Extend PERF_TYPE_HARDWARE and PERF_TYPE_HW_CACHE 2021-04-19 20:03:29 +02:00
gcov Revert "gcov: clang: fix clang-11+ build" 2021-04-19 15:08:49 -07:00
irq The usual updates from the irq departement: 2021-04-26 09:43:16 -07:00
kcsan kcsan: Fix printk format string 2021-04-22 14:36:03 +02:00
livepatch Livepatching changes for 5.13 2021-04-27 18:14:38 -07:00
locking Locking changes for this cycle were: 2021-04-28 12:37:53 -07:00
power PM: sleep: fix typos in comments 2021-04-08 19:37:21 +02:00
printk kernel/printk.c: Fixed mundane typos 2021-03-30 15:34:17 +02:00
rcu Merge branches 'bitmaprange.2021.03.08a', 'fixes.2021.03.15a', 'kvfree_rcu.2021.03.08a', 'mmdumpobj.2021.03.08a', 'nocb.2021.03.15a', 'poll.2021.03.24a', 'rt.2021.03.08a', 'tasks.2021.03.08a', 'torture.2021.03.08a' and 'torturescript.2021.03.22a' into HEAD 2021-03-24 17:20:18 -07:00
sched Scheduler updates for this cycle are: 2021-04-28 13:33:57 -07:00
time Power management updates for 5.13-rc1 2021-04-26 15:10:25 -07:00
trace Networking changes for 5.13. 2021-04-29 11:57:23 -07:00
.gitignore
acct.c kernel/acct.c: use #elif instead of #end and #elif 2020-12-15 22:46:15 -08:00
async.c treewide: Remove uninitialized_var() usage 2020-07-16 12:35:15 -07:00
audit_fsnotify.c audit_alloc_mark(): don't open-code ERR_CAST() 2021-02-23 10:25:27 -05:00
audit_tree.c fsnotify: generalize handle_inode_event() 2020-12-03 14:58:35 +01:00
audit_watch.c fsnotify: generalize handle_inode_event() 2020-12-03 14:58:35 +01:00
audit.c lsm: separate security_task_getsecid() into subjective and objective variants 2021-03-22 15:23:32 -04:00
audit.h audit: avoid -Wempty-body warning 2021-03-24 12:11:48 -04:00
auditfilter.c lsm: separate security_task_getsecid() into subjective and objective variants 2021-03-22 15:23:32 -04:00
auditsc.c audit/stable-5.13 PR 20210426 2021-04-27 13:50:58 -07:00
backtracetest.c treewide: Replace DECLARE_TASKLET() with DECLARE_TASKLET_OLD() 2020-07-30 11:15:58 -07:00
bounds.c
capability.c capability: handle idmapped mounts 2021-01-24 14:27:16 +01:00
cfi.c add support for Clang CFI 2021-04-08 16:04:20 -07:00
compat.c treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
configs.c
context_tracking.c
cpu_pm.c notifier: Fix broken error handling pattern 2020-09-01 09:58:03 +02:00
cpu.c cpumask/hotplug: Fix cpu_dying() state tracking 2021-04-21 13:55:43 +02:00
crash_core.c kdump: append uts_namespace.name offset to VMCOREINFO 2020-12-15 22:46:18 -08:00
crash_dump.c
cred.c
delayacct.c
dma.c
exec_domain.c
exit.c signal: Allow tasks to cache one sigqueue struct 2021-04-14 18:04:08 +02:00
extable.c
fail_function.c fault-injection: handle EI_ETYPE_TRUE 2020-12-15 22:46:19 -08:00
fork.c Networking changes for 5.13. 2021-04-29 11:57:23 -07:00
freezer.c Revert "kernel: freezer should treat PF_IO_WORKER like PF_KTHREAD for freezing" 2021-03-27 14:09:10 -06:00
futex.c Linux 5.12-rc5 2021-03-29 15:56:48 +02:00
gen_kheaders.sh
groups.c groups: simplify struct group_info allocation 2021-02-26 09:41:03 -08:00
hung_task.c kernel/hung_task.c: make type annotations consistent 2020-11-02 12:14:19 -08:00
iomem.c
irq_work.c irq_work: Optimize irq_work_single() 2020-11-24 16:47:49 +01:00
jump_label.c static_call: Fix static_call_update() sanity check 2021-03-19 13:16:44 +01:00
kallsyms.c kallsyms: strip ThinLTO hashes from static functions 2021-04-08 16:04:21 -07:00
kcmp.c Merge branch 'exec-update-lock-for-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2020-12-15 19:36:48 -08:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt preempt: Introduce CONFIG_PREEMPT_DYNAMIC 2021-02-17 14:12:24 +01:00
kcov.c kernel: make kcov_common_handle consider the current context 2020-11-02 18:00:20 -08:00
kexec_core.c Merge branch 'work.elf-compat' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2021-02-21 09:29:23 -08:00
kexec_elf.c
kexec_file.c ima: Free IMA measurement buffer after kexec syscall 2021-02-10 15:49:38 -05:00
kexec_internal.h kexec: move machine_kexec_post_load() to public interface 2021-02-22 12:33:26 +00:00
kexec.c LSM: Introduce kernel_post_load_data() hook 2020-10-05 13:37:03 +02:00
kheaders.c
kmod.c kmod: remove redundant "be an" in the comment 2020-08-12 10:58:01 -07:00
kprobes.c kprobes: Fix to delay the kprobes jump optimization 2021-02-19 14:57:12 -05:00
ksysfs.c
kthread.c Scheduler updates for this cycle are: 2021-04-28 13:33:57 -07:00
latencytop.c
Makefile add support for Clang CFI 2021-04-08 16:04:20 -07:00
module_signature.c module: harden ELF info handling 2021-01-19 10:24:45 +01:00
module_signing.c module: harden ELF info handling 2021-01-19 10:24:45 +01:00
module-internal.h
module.c add support for Clang CFI 2021-04-08 16:04:20 -07:00
notifier.c notifier: Fix broken error handling pattern 2020-09-01 09:58:03 +02:00
nsproxy.c fixes-v5.11 2020-12-14 16:40:27 -08:00
padata.c padata: fix possible padata_works_lock deadlock 2020-09-04 17:51:55 +10:00
panic.c panic: don't dump stack twice on warn 2020-11-14 11:26:04 -08:00
params.c Modules updates for v5.11 2020-12-17 13:01:31 -08:00
pid_namespace.c fixes-v5.11 2020-12-14 16:40:27 -08:00
pid.c Merge branch 'exec-update-lock-for-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2020-12-15 19:36:48 -08:00
profile.c kernel: Initialize cpumask before parsing 2021-04-10 13:35:54 +02:00
ptrace.c Linux 5.12-rc8 2021-04-20 10:13:58 +02:00
range.c kernel.h: split out min()/max() et al. helpers 2020-10-16 11:11:19 -07:00
reboot.c Revert "PM: ACPI: reboot: Use S5 for reboot" 2021-03-18 16:58:02 +01:00
regset.c regset: kill ->get() 2020-07-27 14:31:12 -04:00
relay.c relay: allow the use of const callback structs 2020-12-15 22:46:18 -08:00
resource_kunit.c resource: provide meaningful MODULE_LICENSE() in test suite 2020-11-25 18:52:35 +01:00
resource.c resource: Move devmem revoke code to resource framework 2021-01-12 14:26:31 +01:00
rseq.c rseq: Optimise rseq_get_rseq_cs() and clear_rseq_cs() 2021-04-14 18:04:09 +02:00
scftorture.c scftorture: Add debug output for wrong-CPU warning 2021-01-04 13:53:41 -08:00
scs.c scs: switch to vmapped shadow stacks 2020-12-01 10:30:28 +00:00
seccomp.c seccomp: Fix "cacheable" typo in comments 2021-03-30 22:34:30 -07:00
signal.c Scheduler updates for this cycle are: 2021-04-28 13:33:57 -07:00
smp.c Merge branch 'locking/core' into x86/mm, to resolve conflict 2021-03-06 13:00:58 +01:00
smpboot.c kthread: Extract KTHREAD_IS_PER_CPU 2021-01-22 15:09:42 +01:00
smpboot.h
softirq.c RCU changes for this cycle were: 2021-04-28 12:00:13 -07:00
stackleak.c stackleak: let stack_erasing_sysctl take a kernel pointer buffer 2020-09-19 13:13:39 -07:00
stacktrace.c stacktrace: Remove reliable argument from arch_stack_walk() callback 2020-09-18 14:24:16 +01:00
static_call.c static_call: Fix unused variable warn w/o MODULE 2021-04-09 13:22:12 +02:00
stop_machine.c stop_machine: Add caller debug info to queue_stop_cpus_work 2021-03-23 16:01:58 +01:00
sys_ni.c quota: wire up quotactl_path 2021-03-17 15:51:17 +01:00
sys.c arm64: Introduce prctl(PR_PAC_{SET,GET}_ENABLED_KEYS) 2021-04-13 17:31:44 +01:00
sysctl-test.c
sysctl.c Networking changes for 5.13. 2021-04-29 11:57:23 -07:00
task_work.c task_work: add helper for more targeted task_work canceling 2021-04-11 19:30:25 -06:00
taskstats.c treewide: rename nla_strlcpy to nla_strscpy. 2020-11-16 08:08:54 -08:00
test_kprobes.c
torture.c torture: Replace torture_init_begin string with %s 2021-03-08 14:22:28 -08:00
tracepoint.c tracepoints: Code clean up 2021-02-09 12:27:29 -05:00
tsacct.c
ucount.c fanotify: configurable limits via sysfs 2021-03-16 16:49:31 +01:00
uid16.c
uid16.h
umh.c usermodehelper: reset umask to default before executing user process 2020-10-06 10:31:52 -07:00
up.c smp: Inline on_each_cpu_cond() and on_each_cpu() 2021-03-06 12:59:10 +01:00
user_namespace.c capabilities: require CAP_SETFCAP to map uid 0 2021-04-20 14:28:33 -07:00
user-return-notifier.c
user.c user: Use generic ns_common::count 2020-08-19 14:14:12 +02:00
usermode_driver.c bpf: Fix umd memory leak in copy_process() 2021-03-19 22:23:19 +01:00
utsname_sysctl.c
utsname.c uts: Use generic ns_common::count 2020-08-19 14:13:20 +02:00
watch_queue.c watch_queue: rectify kernel-doc for init_watch() 2021-01-26 11:16:34 +00:00
watchdog_hld.c
watchdog.c workqueue/watchdog: Make unbound workqueues aware of touch_softlockup_watchdog() 2021-04-04 13:26:49 -04:00
workqueue_internal.h
workqueue.c CFI on arm64 series for v5.13-rc1 2021-04-27 10:16:46 -07:00