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Tony Ambardar e23bb04b0c bpf: Fix sysfs export of empty BTF section 
If BTF data is missing or removed from the ELF section it is still exported
via sysfs as a zero-length file:

  root@OpenWrt:/# ls -l /sys/kernel/btf/vmlinux
  -r--r--r--    1 root    root    0 Jul 18 02:59 /sys/kernel/btf/vmlinux

Moreover, reads from this file succeed and leak kernel data:

  root@OpenWrt:/# hexdump -C /sys/kernel/btf/vmlinux|head -10
  000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
  *
  000cc0 00 00 00 00 00 00 00 00 00 00 00 00 80 83 b0 80 |................|
  000cd0 00 10 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
  000ce0 00 00 00 00 00 00 00 00 00 00 00 00 57 ac 6e 9d |............W.n.|
  000cf0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
  *
  002650 00 00 00 00 00 00 00 10 00 00 00 01 00 00 00 01 |................|
  002660 80 82 9a c4 80 85 97 80 81 a9 51 68 00 00 00 02 |..........Qh....|
  002670 80 25 44 dc 80 85 97 80 81 a9 50 24 81 ab c4 60 |.%D.......P$...`|

This situation was first observed with kernel 5.4.x, cross-compiled for a
MIPS target system. Fix by adding a sanity-check for export of zero-length
data sections.

Fixes: 341dfcf8d78e ("btf: expose BTF info through sysfs")
Signed-off-by: Tony Ambardar <Tony.Ambardar@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/b38db205a66238f70823039a8c531535864eaac5.1600417359.git.Tony.Ambardar@gmail.com
2020-09-21 21:50:24 +02:00
..
bpf
bpf: Fix sysfs export of empty BTF section
2020-09-21 21:50:24 +02:00
cgroup
for-5.9/block-20200802
2020-08-03 11:57:03 -07:00
configs
compiler: remove CONFIG_OPTIMIZE_INLINING entirely
2020-04-07 10:43:42 -07:00
debug
treewide: Use fallthrough pseudo-keyword
2020-08-23 17:36:59 -05:00
dma
dma-pool: Fix an uninitialized variable bug in atomic_pool_expand()
2020-08-27 09:22:56 +02:00
entry
core/entry: Respect syscall number rewrites
2020-08-21 16:17:29 +02:00
events
treewide: Use fallthrough pseudo-keyword
2020-08-23 17:36:59 -05:00
gcov
gcov: Disable gcov build with GCC 10
2020-09-04 09:19:49 -07:00
irq
Three interrupt related fixes for X86:
2020-08-30 12:01:23 -07:00
kcsan
Merge branch 'kcsan' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into locking/core
2020-08-01 09:26:27 +02:00
livepatch
livepatch: Make klp_apply_object_relocs static
2020-05-11 00:31:38 +02:00
locking
lockdep,trace: Expose tracepoints
2020-08-26 12:41:56 +02:00
power
treewide: Use fallthrough pseudo-keyword
2020-08-23 17:36:59 -05:00
printk
Printk changes for 5.9
2020-08-04 22:22:25 -07:00
rcu
rcu: kasan: record and print call_rcu() call stack
2020-08-07 11:33:28 -07:00
sched
A set of fixes for lockdep, tracing and RCU:
2020-08-30 11:43:50 -07:00
time
treewide: Use fallthrough pseudo-keyword
2020-08-23 17:36:59 -05:00
trace
treewide: Use fallthrough pseudo-keyword
2020-08-23 17:36:59 -05:00
.gitignore
.gitignore: add SPDX License Identifier
2020-03-25 11:50:48 +01:00
acct.c
mmap locking API: convert mmap_sem comments
2020-06-09 09:39:14 -07:00
async.c
treewide: Remove uninitialized_var() usage
2020-07-16 12:35:15 -07:00
audit_fsnotify.c
fsnotify: create method handle_inode_event() in fsnotify_operations
2020-07-27 23:25:50 +02:00
audit_tree.c
\n
2020-08-06 19:29:51 -07:00
audit_watch.c
fsnotify: create method handle_inode_event() in fsnotify_operations
2020-07-27 23:25:50 +02:00
audit.c
audit/stable-5.9 PR 20200803
2020-08-04 14:20:26 -07:00
audit.h
revert: 1320a4052ea1 ("audit: trigger accompanying records when no rules present")
2020-07-29 10:00:36 -04:00
auditfilter.c
treewide: Use fallthrough pseudo-keyword
2020-08-23 17:36:59 -05:00
auditsc.c
audit/stable-5.9 PR 20200803
2020-08-04 14:20:26 -07:00
backtracetest.c
treewide: Replace DECLARE_TASKLET() with DECLARE_TASKLET_OLD()
2020-07-30 11:15:58 -07:00
bounds.c
…
capability.c
treewide: Use fallthrough pseudo-keyword
2020-08-23 17:36:59 -05:00
compat.c
treewide: Use fallthrough pseudo-keyword
2020-08-23 17:36:59 -05:00
configs.c
proc: convert everything to "struct proc_ops"
2020-02-04 03:05:26 +00:00
context_tracking.c
context_tracking: Ensure that the critical path cannot be instrumented
2020-06-11 15:14:36 +02:00
cpu_pm.c
kernel/cpu_pm: Fix uninitted local in cpu_pm
2020-05-15 11:44:34 -07:00
cpu.c
The changes in this cycle are:
2020-06-03 13:06:42 -07:00
crash_core.c
kdump: append kernel build-id string to VMCOREINFO
2020-08-12 10:58:01 -07:00
crash_dump.c
crash_dump: Remove no longer used saved_max_pfn
2020-04-15 11:21:54 +02:00
cred.c
exec: Teach prepare_exec_creds how exec treats uids & gids
2020-05-20 14:44:21 -05:00
delayacct.c
…
dma.c
…
elfcore.c
…
exec_domain.c
…
exit.c
kernel: add a kernel_wait helper
2020-08-12 10:57:59 -07:00
extable.c
kernel/extable.c: use address-of operator on section symbols
2020-04-07 10:43:42 -07:00
fail_function.c
…
fork.c
A set of locking fixes and updates:
2020-08-10 19:07:44 -07:00
freezer.c
…
futex.c
futex: Convert to use the preferred 'fallthrough' macro
2020-08-13 21:02:12 +02:00
gen_kheaders.sh
kbuild: add variables for compression tools
2020-06-06 23:42:01 +09:00
groups.c
mm: remove the pgprot argument to __vmalloc
2020-06-02 10:59:11 -07:00
hung_task.c
kernel/hung_task.c: introduce sysctl to print all traces when a hung task is detected
2020-06-08 11:05:56 -07:00
iomem.c
…
irq_work.c
irq_work, smp: Allow irq_work on call_single_queue
2020-05-28 10:54:15 +02:00
jump_label.c
…
kallsyms.c
treewide: Use fallthrough pseudo-keyword
2020-08-23 17:36:59 -05:00
kcmp.c
kernel/kcmp.c: Use new infrastructure to fix deadlocks in execve
2020-03-25 10:04:01 -05:00
Kconfig.freezer
…
Kconfig.hz
…
Kconfig.locks
…
Kconfig.preempt
…
kcov.c
kcov: make some symbols static
2020-08-12 10:58:02 -07:00
kexec_core.c
kexec: add machine_kexec_post_load()
2020-01-08 16:32:55 +00:00
kexec_elf.c
…
kexec_file.c
Misc fixes and small updates all around the place:
2020-08-15 10:38:03 -07:00
kexec_internal.h
kexec: add machine_kexec_post_load()
2020-01-08 16:32:55 +00:00
kexec.c
kexec: add machine_kexec_post_load()
2020-01-08 16:32:55 +00:00
kheaders.c
…
kmod.c
kmod: remove redundant "be an" in the comment
2020-08-12 10:58:01 -07:00
kprobes.c
Tracing updates for 5.9
2020-08-07 18:29:15 -07:00
ksysfs.c
…
kthread.c
uaccess: add force_uaccess_{begin,end} helpers
2020-08-12 10:57:59 -07:00
latencytop.c
sysctl: pass kernel pointers to ->proc_handler
2020-04-27 02:07:40 -04:00
Makefile
all arch: remove system call sys_sysctl
2020-08-14 19:56:56 -07:00
module_signature.c
…
module_signing.c
…
module-internal.h
…
module.c
Modules updates for v5.9
2020-08-14 11:07:02 -07:00
notifier.c
mm: remove vmalloc_sync_(un)mappings()
2020-06-02 10:59:12 -07:00
nsproxy.c
nsproxy: support CLONE_NEWTIME with setns()
2020-07-08 11:14:22 +02:00
padata.c
padata: remove padata_parallel_queue
2020-07-23 17:34:18 +10:00
panic.c
panic: make print_oops_end_marker() static
2020-08-12 10:58:02 -07:00
params.c
…
pid_namespace.c
pid_namespace: use checkpoint_restore_ns_capable() for ns_last_pid
2020-07-19 20:14:42 +02:00
pid.c
cap-checkpoint-restore-v5.9
2020-08-04 15:02:07 -07:00
profile.c
proc: convert everything to "struct proc_ops"
2020-02-04 03:05:26 +00:00
ptrace.c
ptrace: reintroduce usage of subjective credentials in ptrace_has_cap()
2020-01-18 13:51:39 +01:00
range.c
…
reboot.c
arch: remove unicore32 port
2020-07-01 12:09:13 +03:00
regset.c
regset: kill ->get()
2020-07-27 14:31:12 -04:00
relay.c
kernel/relay.c: fix memleak on destroy relay channel
2020-08-21 09:52:53 -07:00
resource.c
/dev/mem: Revoke mappings when a driver claims the region
2020-05-27 11:10:05 +02:00
rseq.c
rseq: Reject unknown flags on rseq unregister
2019-12-25 10:41:20 +01:00
scs.c
mm: memcontrol: account kernel stack per node
2020-08-07 11:33:25 -07:00
seccomp.c
seccomp: Introduce addfd ioctl to seccomp user notifier
2020-07-14 16:29:42 -07:00
signal.c
treewide: Use fallthrough pseudo-keyword
2020-08-23 17:36:59 -05:00
smp.c
smp: Fix a potential usage of stale nr_cpus
2020-07-22 10:22:04 +02:00
smpboot.c
…
smpboot.h
…
softirq.c
tasklets API update for v5.9-rc1
2020-08-04 13:40:35 -07:00
stackleak.c
gcc-plugins/stackleak: Use asm instrumentation to avoid useless register saving
2020-06-24 07:48:28 -07:00
stacktrace.c
uaccess: add force_uaccess_{begin,end} helpers
2020-08-12 10:57:59 -07:00
stop_machine.c
stop_machine: Make stop_cpus() static
2020-01-17 10:19:21 +01:00
sys_ni.c
all arch: remove system call sys_sysctl
2020-08-14 19:56:56 -07:00
sys.c
treewide: Use fallthrough pseudo-keyword
2020-08-23 17:36:59 -05:00
sysctl-test.c
kunit: allow kunit tests to be loaded as a module
2020-01-09 16:42:29 -07:00
sysctl.c
bpf, sysctl: Let bpf_stats_handler take a kernel pointer buffer
2020-08-24 21:11:40 -07:00
task_work.c
task_work: only grab task signal lock when needed
2020-08-13 09:01:38 -06:00
taskstats.c
…
test_kprobes.c
…
torture.c
torture: Dump ftrace at shutdown only if requested
2020-06-29 12:01:45 -07:00
tracepoint.c
…
tsacct.c
tsacct: add 64-bit btime field
2019-12-18 18:07:31 +01:00
ucount.c
ucount: Make sure ucounts in /proc/sys/user don't regress again
2020-04-07 21:51:27 +02:00
uid16.c
…
uid16.h
…
umh.c
kernel: add a kernel_wait helper
2020-08-12 10:57:59 -07:00
up.c
smp/up: Make smp_call_function_single() match SMP semantics
2020-02-07 15:34:12 +01:00
user_namespace.c
nsproxy: add struct nsset
2020-05-09 13:57:12 +02:00
user-return-notifier.c
…
user.c
user.c: make uidhash_table static
2020-06-04 19:06:24 -07:00
usermode_driver.c
umd: Stop using split_argv
2020-07-07 11:58:59 -05:00
utsname_sysctl.c
sysctl: pass kernel pointers to ->proc_handler
2020-04-27 02:07:40 -04:00
utsname.c
nsproxy: add struct nsset
2020-05-09 13:57:12 +02:00
watch_queue.c
watch_queue: Limit the number of watches a user can hold
2020-08-17 09:39:18 -07:00
watchdog_hld.c
…
watchdog.c
kernel/watchdog.c: convert {soft/hard}lockup boot parameters to sysctl aliases
2020-06-08 11:05:56 -07:00
workqueue_internal.h
…
workqueue.c
maccess: rename probe_kernel_{read,write} to copy_{from,to}_kernel_nofault
2020-06-17 10:57:41 -07:00