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linux/kernel/bpf
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Kumar Kartikeya Dwivedi ec5290a178 bpf: Prevent KASAN false positive with bpf_throw 
The KASAN stack instrumentation when CONFIG_KASAN_STACK is true poisons
the stack of a function when it is entered and unpoisons it when
leaving. However, in the case of bpf_throw, we will never return as we
switch our stack frame to the BPF exception callback. Later, this
discrepancy will lead to confusing KASAN splats when kernel resumes
execution on return from the BPF program.

Fix this by unpoisoning everything below the stack pointer of the BPF
program, which should cover the range that would not be unpoisoned. An
example splat is below:

BUG: KASAN: stack-out-of-bounds in stack_trace_consume_entry+0x14e/0x170
Write of size 8 at addr ffffc900013af958 by task test_progs/227

CPU: 0 PID: 227 Comm: test_progs Not tainted 6.5.0-rc2-g43f1c6c9052a-dirty #26
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-2.fc39 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0x4a/0x80
 print_report+0xcf/0x670
 ? arch_stack_walk+0x79/0x100
 kasan_report+0xda/0x110
 ? stack_trace_consume_entry+0x14e/0x170
 ? stack_trace_consume_entry+0x14e/0x170
 ? __pfx_stack_trace_consume_entry+0x10/0x10
 stack_trace_consume_entry+0x14e/0x170
 ? __sys_bpf+0xf2e/0x41b0
 arch_stack_walk+0x8b/0x100
 ? __sys_bpf+0xf2e/0x41b0
 ? bpf_prog_test_run_skb+0x341/0x1c70
 ? bpf_prog_test_run_skb+0x341/0x1c70
 stack_trace_save+0x9b/0xd0
 ? __pfx_stack_trace_save+0x10/0x10
 ? __kasan_slab_free+0x109/0x180
 ? bpf_prog_test_run_skb+0x341/0x1c70
 ? __sys_bpf+0xf2e/0x41b0
 ? __x64_sys_bpf+0x78/0xc0
 ? do_syscall_64+0x3c/0x90
 ? entry_SYSCALL_64_after_hwframe+0x6e/0xd8
 kasan_save_stack+0x33/0x60
 ? kasan_save_stack+0x33/0x60
 ? kasan_set_track+0x25/0x30
 ? kasan_save_free_info+0x2b/0x50
 ? __kasan_slab_free+0x109/0x180
 ? kmem_cache_free+0x191/0x460
 ? bpf_prog_test_run_skb+0x341/0x1c70
 kasan_set_track+0x25/0x30
 kasan_save_free_info+0x2b/0x50
 __kasan_slab_free+0x109/0x180
 kmem_cache_free+0x191/0x460
 bpf_prog_test_run_skb+0x341/0x1c70
 ? __pfx_bpf_prog_test_run_skb+0x10/0x10
 ? __fget_light+0x51/0x220
 __sys_bpf+0xf2e/0x41b0
 ? __might_fault+0xa2/0x170
 ? __pfx___sys_bpf+0x10/0x10
 ? lock_release+0x1de/0x620
 ? __might_fault+0xcd/0x170
 ? __pfx_lock_release+0x10/0x10
 ? __pfx_blkcg_maybe_throttle_current+0x10/0x10
 __x64_sys_bpf+0x78/0xc0
 ? syscall_enter_from_user_mode+0x20/0x50
 do_syscall_64+0x3c/0x90
 entry_SYSCALL_64_after_hwframe+0x6e/0xd8
RIP: 0033:0x7f0fbb38880d
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d
89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d f3 45 12 00 f7 d8 64
89 01 48
RSP: 002b:00007ffe13907de8 EFLAGS: 00000206 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007ffe13908708 RCX: 00007f0fbb38880d
RDX: 0000000000000050 RSI: 00007ffe13907e20 RDI: 000000000000000a
RBP: 00007ffe13907e00 R08: 0000000000000000 R09: 00007ffe13907e20
R10: 0000000000000064 R11: 0000000000000206 R12: 0000000000000003
R13: 0000000000000000 R14: 00007f0fbb532000 R15: 0000000000cfbd90
 </TASK>

The buggy address belongs to stack of task test_progs/227
KASAN internal error: frame info validation failed; invalid marker: 0

The buggy address belongs to the virtual mapping at
 [ffffc900013a8000, ffffc900013b1000) created by:
 kernel_clone+0xcd/0x600

The buggy address belongs to the physical page:
page:00000000b70f4332 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x11418f
flags: 0x2fffe0000000000(node=0|zone=2|lastcpupid=0x7fff)
page_type: 0xffffffff()
raw: 02fffe0000000000 0000000000000000 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffffc900013af800: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffc900013af880: 00 00 00 f1 f1 f1 f1 00 00 00 f3 f3 f3 f3 f3 00
>ffffc900013af900: 00 00 00 00 00 00 00 00 00 00 00 f1 00 00 00 00
                                                    ^
 ffffc900013af980: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffc900013afa00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================
Disabling lock debugging due to kernel taint

Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Acked-by: Andrey Konovalov <andreyknvl@gmail.com>
Link: https://lore.kernel.org/r/20230912233214.1518551-11-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2023-09-16 09:34:22 -07:00
..
preload bpf: make preloaded map iterators to display map elements count 2023-07-06 12:42:25 -07:00
arraymap.c bpf: return long from bpf_map_ops funcs 2023-03-22 15:11:30 -07:00
bloom_filter.c bpf: Centralize permissions checks for all BPF map types 2023-06-19 14:04:04 +02:00
bpf_cgrp_storage.c bpf: Teach verifier that certain helpers accept NULL pointer. 2023-04-04 16:57:16 -07:00
bpf_inode_storage.c Networking changes for 6.4. 2023-04-26 16:07:23 -07:00
bpf_iter.c bpf: implement numbers iterator 2023-03-08 16:19:51 -08:00
bpf_local_storage.c bpf: bpf_sk_storage: Fix the missing uncharge in sk_omem_alloc 2023-09-06 11:08:14 +02:00
bpf_lru_list.c bpf: Address KCSAN report on bpf_lru_list 2023-05-12 12:01:03 -07:00
bpf_lru_list.h bpf: lru: Remove unused declaration bpf_lru_promote() 2023-08-08 17:21:42 -07:00
bpf_lsm.c bpf: Fix the kernel crash caused by bpf_setsockopt(). 2023-01-26 23:26:40 -08:00
bpf_struct_ops.c bpf: Charge modmem for struct_ops trampoline 2023-09-14 15:30:45 -07:00
bpf_struct_ops_types.h
bpf_task_storage.c bpf: Teach verifier that certain helpers accept NULL pointer. 2023-04-04 16:57:16 -07:00
btf.c bpf: Add support for custom exception callbacks 2023-09-16 09:34:21 -07:00
cgroup.c bpf-next-for-netdev 2023-05-16 19:50:05 -07:00
cgroup_iter.c cgroup: bpf: use cgroup_lock()/cgroup_unlock() wrappers 2023-03-17 12:07:13 -10:00
core.c bpf: Implement BPF exceptions 2023-09-16 09:34:21 -07:00
cpumap.c bpf, cpumask: Clean up bpf_cpu_map_entry directly in cpu_map_free 2023-08-21 15:21:16 -07:00
cpumask.c bpf: Convert bpf_cpumask to bpf_mem_cache_free_rcu. 2023-07-12 23:45:23 +02:00
devmap.c bpf, devmap: Remove unused dtab field from bpf_dtab_netdev 2023-07-31 18:26:08 -07:00
disasm.c bpf: change bpf_alu_sign_string and bpf_movsx_string to static 2023-08-04 16:15:50 -07:00
disasm.h
dispatcher.c bpf: Synchronize dispatcher update with bpf_dispatcher_xdp_func 2022-12-14 12:02:14 -08:00
hashtab.c bpf: populate the per-cpu insertions/deletions counters for hashmaps 2023-07-06 12:42:25 -07:00
helpers.c bpf: Prevent KASAN false positive with bpf_throw 2023-09-16 09:34:22 -07:00
inode.c bpf: convert to ctime accessor functions 2023-07-24 10:30:07 +02:00
Kconfig bpf: Add fd-based tcx multi-prog infra with link support 2023-07-19 10:07:27 -07:00
link_iter.c
local_storage.c cgroup changes for v6.4-rc1 2023-04-29 10:05:22 -07:00
log.c bpf: drop unnecessary user-triggerable WARN_ONCE in verifierl log 2023-05-16 22:34:50 -07:00
lpm_trie.c bpf: Centralize permissions checks for all BPF map types 2023-06-19 14:04:04 +02:00
Makefile bpf: Add fd-based tcx multi-prog infra with link support 2023-07-19 10:07:27 -07:00
map_in_map.c bpf: Fix elem_size not being set for inner maps 2023-06-02 16:22:12 -07:00
map_in_map.h
map_iter.c bpf: allow any program to use the bpf_map_sum_elem_count kfunc 2023-07-19 09:48:53 -07:00
memalloc.c bpf: Enable IRQ after irq_work_raise() completes in unit_free{_rcu}() 2023-09-08 08:42:19 -07:00
mmap_unlock_work.h
mprog.c bpf: Fix mprog detachment for empty mprog entry 2023-08-04 09:35:39 -07:00
net_namespace.c
offload.c bpf: Allow to use kfunc XDP hints and frags together 2023-09-15 11:39:46 -07:00
percpu_freelist.c bpf: Initialize same number of free nodes for each pcpu_freelist 2022-11-11 12:05:14 -08:00
percpu_freelist.h
prog_iter.c
queue_stack_maps.c bpf: Centralize permissions checks for all BPF map types 2023-06-19 14:04:04 +02:00
reuseport_array.c bpf: Centralize permissions checks for all BPF map types 2023-06-19 14:04:04 +02:00
ringbuf.c bpf: Remove unnecessary ring buffer size check 2023-07-05 14:09:45 +02:00
stackmap.c bpf: Centralize permissions checks for all BPF map types 2023-06-19 14:04:04 +02:00
syscall.c bpf: Implement support for adding hidden subprogs 2023-09-16 09:34:21 -07:00
sysfs_btf.c
task_iter.c bpf: task_group_seq_get_next: simplify the "next tid" logic 2023-09-08 08:42:19 -07:00
tcx.c tcx: Fix splat during dev unregister 2023-07-31 14:44:02 -07:00
tnum.c
trampoline.c bpf, x64: Fix tailcall infinite loop 2023-09-12 13:06:12 -07:00
verifier.c bpf: Treat first argument as return value for bpf_throw 2023-09-16 09:34:21 -07:00