linux-stable.git/kernel/bpf/core.c, branch v6.1.136

bpf: Prevent tail call between progs attached to different hooks

2025-04-25T08:44:03+00:00

commit 28ead3eaabc16ecc907cfb71876da028080f6356 upstream.

bpf progs can be attached to kernel functions, and the attached functions
can take different parameters or return different return values. If
prog attached to one kernel function tail calls prog attached to another
kernel function, the ctx access or return value verification could be
bypassed.

For example, if prog1 is attached to func1 which takes only 1 parameter
and prog2 is attached to func2 which takes two parameters. Since verifier
assumes the bpf ctx passed to prog2 is constructed based on func2's
prototype, verifier allows prog2 to access the second parameter from
the bpf ctx passed to it. The problem is that verifier does not prevent
prog1 from passing its bpf ctx to prog2 via tail call. In this case,
the bpf ctx passed to prog2 is constructed from func1 instead of func2,
that is, the assumption for ctx access verification is bypassed.

Another example, if BPF LSM prog1 is attached to hook file_alloc_security,
and BPF LSM prog2 is attached to hook bpf_lsm_audit_rule_known. Verifier
knows the return value rules for these two hooks, e.g. it is legal for
bpf_lsm_audit_rule_known to return positive number 1, and it is illegal
for file_alloc_security to return positive number. So verifier allows
prog2 to return positive number 1, but does not allow prog1 to return
positive number. The problem is that verifier does not prevent prog1
from calling prog2 via tail call. In this case, prog2's return value 1
will be used as the return value for prog1's hook file_alloc_security.
That is, the return value rule is bypassed.

This patch adds restriction for tail call to prevent such bypasses.

Signed-off-by: Xu Kuohai 
Link: https://lore.kernel.org/r/20240719110059.797546-4-xukuohai@huaweicloud.com
Signed-off-by: Alexei Starovoitov 
Signed-off-by: Andrii Nakryiko 
[Minor conflict resolved due to code context change.]
Signed-off-by: Jianqi Ren 
Signed-off-by: He Zhe 
Signed-off-by: Greg Kroah-Hartman

bpf: fix potential error return

2025-01-09T12:30:04+00:00

[ Upstream commit c4441ca86afe4814039ee1b32c39d833c1a16bbc ]

The bpf_remove_insns() function returns WARN_ON_ONCE(error), where
error is a result of bpf_adj_branches(), and thus should be always 0
However, if for any reason it is not 0, then it will be converted to
boolean by WARN_ON_ONCE and returned to user space as 1, not an actual
error value. Fix this by returning the original err after the WARN check.

Signed-off-by: Anton Protopopov 
Acked-by: Jiri Olsa 
Acked-by: Andrii Nakryiko 
Link: https://lore.kernel.org/r/20241210114245.836164-1-aspsk@isovalent.com
Signed-off-by: Alexei Starovoitov 
Signed-off-by: Sasha Levin

bpf: Mark bpf prog stack with kmsan_unposion_memory in interpreter mode

2024-07-05T07:31:48+00:00

[ Upstream commit e8742081db7d01f980c6161ae1e8a1dbc1e30979 ]

syzbot reported uninit memory usages during map_{lookup,delete}_elem.

==========
BUG: KMSAN: uninit-value in __dev_map_lookup_elem kernel/bpf/devmap.c:441 [inline]
BUG: KMSAN: uninit-value in dev_map_lookup_elem+0xf3/0x170 kernel/bpf/devmap.c:796
__dev_map_lookup_elem kernel/bpf/devmap.c:441 [inline]
dev_map_lookup_elem+0xf3/0x170 kernel/bpf/devmap.c:796
____bpf_map_lookup_elem kernel/bpf/helpers.c:42 [inline]
bpf_map_lookup_elem+0x5c/0x80 kernel/bpf/helpers.c:38
___bpf_prog_run+0x13fe/0xe0f0 kernel/bpf/core.c:1997
__bpf_prog_run256+0xb5/0xe0 kernel/bpf/core.c:2237
==========

The reproducer should be in the interpreter mode.

The C reproducer is trying to run the following bpf prog:

    0: (18) r0 = 0x0
    2: (18) r1 = map[id:49]
    4: (b7) r8 = 16777216
    5: (7b) *(u64 *)(r10 -8) = r8
    6: (bf) r2 = r10
    7: (07) r2 += -229
            ^^^^^^^^^^

    8: (b7) r3 = 8
    9: (b7) r4 = 0
   10: (85) call dev_map_lookup_elem#1543472
   11: (95) exit

It is due to the "void *key" (r2) passed to the helper. bpf allows uninit
stack memory access for bpf prog with the right privileges. This patch
uses kmsan_unpoison_memory() to mark the stack as initialized.

This should address different syzbot reports on the uninit "void *key"
argument during map_{lookup,delete}_elem.

Reported-by: syzbot+603bcd9b0bf1d94dbb9b@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/bpf/000000000000f9ce6d061494e694@google.com/
Reported-by: syzbot+eb02dc7f03dce0ef39f3@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/bpf/000000000000a5c69c06147c2238@google.com/
Reported-by: syzbot+b4e65ca24fd4d0c734c3@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/bpf/000000000000ac56fb06143b6cfa@google.com/
Reported-by: syzbot+d2b113dc9fea5e1d2848@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/bpf/0000000000000d69b206142d1ff7@google.com/
Reported-by: syzbot+1a3cf6f08d68868f9db3@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/bpf/0000000000006f876b061478e878@google.com/
Tested-by: syzbot+1a3cf6f08d68868f9db3@syzkaller.appspotmail.com
Suggested-by: Yonghong Song 
Suggested-by: Alexei Starovoitov 
Signed-off-by: Martin KaFai Lau 
Link: https://lore.kernel.org/r/20240328185801.1843078-1-martin.lau@linux.dev
Signed-off-by: Alexei Starovoitov 
Signed-off-by: Sasha Levin

bpf: Take return from set_memory_ro() into account with bpf_prog_lock_ro()

2024-07-05T07:31:47+00:00

[ Upstream commit 7d2cc63eca0c993c99d18893214abf8f85d566d8 ]

set_memory_ro() can fail, leaving memory unprotected.

Check its return and take it into account as an error.

Link: https://github.com/KSPP/linux/issues/7
Signed-off-by: Christophe Leroy 
Cc: linux-hardening@vger.kernel.org 
Reviewed-by: Kees Cook 
Message-ID: <286def78955e04382b227cb3e4b6ba272a7442e3.1709850515.git.christophe.leroy@csgroup.eu>
Signed-off-by: Alexei Starovoitov 
Signed-off-by: Sasha Levin

bpf: hardcode BPF_PROG_PACK_SIZE to 2MB * num_possible_nodes()

2024-03-26T22:20:43+00:00

[ Upstream commit d6170e4aaf86424c24ce06e355b4573daa891b17 ]

On some architectures like ARM64, PMD_SIZE can be really large in some
configurations. Like with CONFIG_ARM64_64K_PAGES=y the PMD_SIZE is
512MB.

Use 2MB * num_possible_nodes() as the size for allocations done through
the prog pack allocator. On most architectures, PMD_SIZE will be equal
to 2MB in case of 4KB pages and will be greater than 2MB for bigger page
sizes.

Fixes: ea2babac63d4 ("bpf: Simplify bpf_prog_pack_[size|mask]")
Reported-by: "kernelci.org bot" 
Closes: https://lore.kernel.org/all/7e216c88-77ee-47b8-becc-a0f780868d3c@sirena.org.uk/
Reported-by: kernel test robot 
Closes: https://lore.kernel.org/oe-kbuild-all/202403092219.dhgcuz2G-lkp@intel.com/
Suggested-by: Song Liu 
Signed-off-by: Puranjay Mohan 
Message-ID: <20240311122722.86232-1-puranjay12@gmail.com>
Signed-off-by: Alexei Starovoitov 
Signed-off-by: Sasha Levin

bpf: Fix a verifier bug due to incorrect branch offset comparison with cpu=v4

2024-01-10T16:10:36+00:00

commit dfce9cb3140592b886838e06f3e0c25fea2a9cae upstream.

Bpf cpu=v4 support is introduced in [1] and Commit 4cd58e9af8b9
("bpf: Support new 32bit offset jmp instruction") added support for new
32bit offset jmp instruction. Unfortunately, in function
bpf_adj_delta_to_off(), for new branch insn with 32bit offset, the offset
(plus/minor a small delta) compares to 16-bit offset bound
[S16_MIN, S16_MAX], which caused the following verification failure:
  $ ./test_progs-cpuv4 -t verif_scale_pyperf180
  ...
  insn 10 cannot be patched due to 16-bit range
  ...
  libbpf: failed to load object 'pyperf180.bpf.o'
  scale_test:FAIL:expect_success unexpected error: -12 (errno 12)
  #405     verif_scale_pyperf180:FAIL

Note that due to recent llvm18 development, the patch [2] (already applied
in bpf-next) needs to be applied to bpf tree for testing purpose.

The fix is rather simple. For 32bit offset branch insn, the adjusted
offset compares to [S32_MIN, S32_MAX] and then verification succeeded.

  [1] https://lore.kernel.org/all/20230728011143.3710005-1-yonghong.song@linux.dev
  [2] https://lore.kernel.org/bpf/20231110193644.3130906-1-yonghong.song@linux.dev

Fixes: 4cd58e9af8b9 ("bpf: Support new 32bit offset jmp instruction")
Signed-off-by: Yonghong Song 
Signed-off-by: Andrii Nakryiko 
Link: https://lore.kernel.org/bpf/20231201024640.3417057-1-yonghong.song@linux.dev
Signed-off-by: Greg Kroah-Hartman

bpf: Support new 32bit offset jmp instruction

2024-01-10T16:10:29+00:00

[ Upstream commit 4cd58e9af8b9d9fff6b7145e742abbfcda0af4af ]

Add interpreter/jit/verifier support for 32bit offset jmp instruction.
If a conditional jmp instruction needs more than 16bit offset,
it can be simulated with a conditional jmp + a 32bit jmp insn.

Acked-by: Eduard Zingerman 
Signed-off-by: Yonghong Song 
Link: https://lore.kernel.org/r/20230728011231.3716103-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov 
Stable-dep-of: 3feb263bb516 ("bpf: handle ldimm64 properly in check_cfg()")
Signed-off-by: Sasha Levin

bpf: Detect IP == ksym.end as part of BPF program

2023-11-28T17:06:55+00:00

[ Upstream commit 66d9111f3517f85ef2af0337ece02683ce0faf21 ]

Now that bpf_throw kfunc is the first such call instruction that has
noreturn semantics within the verifier, this also kicks in dead code
elimination in unprecedented ways. For one, any instruction following
a bpf_throw call will never be marked as seen. Moreover, if a callchain
ends up throwing, any instructions after the call instruction to the
eventually throwing subprog in callers will also never be marked as
seen.

The tempting way to fix this would be to emit extra 'int3' instructions
which bump the jited_len of a program, and ensure that during runtime
when a program throws, we can discover its boundaries even if the call
instruction to bpf_throw (or to subprogs that always throw) is emitted
as the final instruction in the program.

An example of such a program would be this:

do_something():
	...
	r0 = 0
	exit

foo():
	r1 = 0
	call bpf_throw
	r0 = 0
	exit

bar(cond):
	if r1 != 0 goto pc+2
	call do_something
	exit
	call foo
	r0 = 0  // Never seen by verifier
	exit	//

main(ctx):
	r1 = ...
	call bar
	r0 = 0
	exit

Here, if we do end up throwing, the stacktrace would be the following:

bpf_throw
foo
bar
main

In bar, the final instruction emitted will be the call to foo, as such,
the return address will be the subsequent instruction (which the JIT
emits as int3 on x86). This will end up lying outside the jited_len of
the program, thus, when unwinding, we will fail to discover the return
address as belonging to any program and end up in a panic due to the
unreliable stack unwinding of BPF programs that we never expect.

To remedy this case, make bpf_prog_ksym_find treat IP == ksym.end as
part of the BPF program, so that is_bpf_text_address returns true when
such a case occurs, and we are able to unwind reliably when the final
instruction ends up being a call instruction.

Signed-off-by: Kumar Kartikeya Dwivedi 
Link: https://lore.kernel.org/r/20230912233214.1518551-12-memxor@gmail.com
Signed-off-by: Alexei Starovoitov 
Signed-off-by: Sasha Levin

bpf: Adjust insufficient default bpf_jit_limit

2023-03-30T10:49:08+00:00

[ Upstream commit 10ec8ca8ec1a2f04c4ed90897225231c58c124a7 ]

We've seen recent AWS EKS (Kubernetes) user reports like the following:

  After upgrading EKS nodes from v20230203 to v20230217 on our 1.24 EKS
  clusters after a few days a number of the nodes have containers stuck
  in ContainerCreating state or liveness/readiness probes reporting the
  following error:

    Readiness probe errored: rpc error: code = Unknown desc = failed to
    exec in container: failed to start exec "4a11039f730203ffc003b7[...]":
    OCI runtime exec failed: exec failed: unable to start container process:
    unable to init seccomp: error loading seccomp filter into kernel:
    error loading seccomp filter: errno 524: unknown

  However, we had not been seeing this issue on previous AMIs and it only
  started to occur on v20230217 (following the upgrade from kernel 5.4 to
  5.10) with no other changes to the underlying cluster or workloads.

  We tried the suggestions from that issue (sysctl net.core.bpf_jit_limit=452534528)
  which helped to immediately allow containers to be created and probes to
  execute but after approximately a day the issue returned and the value
  returned by cat /proc/vmallocinfo | grep bpf_jit | awk '{s+=$2} END {print s}'
  was steadily increasing.

I tested bpf tree to observe bpf_jit_charge_modmem, bpf_jit_uncharge_modmem
their sizes passed in as well as bpf_jit_current under tcpdump BPF filter,
seccomp BPF and native (e)BPF programs, and the behavior all looks sane
and expected, that is nothing "leaking" from an upstream perspective.

The bpf_jit_limit knob was originally added in order to avoid a situation
where unprivileged applications loading BPF programs (e.g. seccomp BPF
policies) consuming all the module memory space via BPF JIT such that loading
of kernel modules would be prevented. The default limit was defined back in
2018 and while good enough back then, we are generally seeing far more BPF
consumers today.

Adjust the limit for the BPF JIT pool from originally 1/4 to now 1/2 of the
module memory space to better reflect today's needs and avoid more users
running into potentially hard to debug issues.

Fixes: fdadd04931c2 ("bpf: fix bpf_jit_limit knob for PAGE_SIZE >= 64K")
Reported-by: Stephen Haynes 
Reported-by: Lefteris Alexakis 
Signed-off-by: Daniel Borkmann 
Link: https://github.com/awslabs/amazon-eks-ami/issues/1179
Link: https://github.com/awslabs/amazon-eks-ami/issues/1219
Reviewed-by: Kuniyuki Iwashima 
Link: https://lore.kernel.org/r/20230320143725.8394-1-daniel@iogearbox.net
Signed-off-by: Alexei Starovoitov 
Signed-off-by: Sasha Levin

bpf: add missing header file include

2023-02-25T10:25:43+00:00

commit f3dd0c53370e70c0f9b7e931bbec12916f3bb8cc upstream.

Commit 74e19ef0ff80 ("uaccess: Add speculation barrier to
copy_from_user()") built fine on x86-64 and arm64, and that's the extent
of my local build testing.

It turns out those got the  include incidentally through
other header files ( in particular), but that was not
true of other architectures, resulting in build errors

  kernel/bpf/core.c: In function ‘___bpf_prog_run’:
  kernel/bpf/core.c:1913:3: error: implicit declaration of function ‘barrier_nospec’

so just make sure to explicitly include the proper 
header file to make everybody see it.

Fixes: 74e19ef0ff80 ("uaccess: Add speculation barrier to copy_from_user()")
Reported-by: kernel test robot 
Reported-by: Viresh Kumar 
Reported-by: Huacai Chen 
Tested-by: Geert Uytterhoeven 
Tested-by: Dave Hansen 
Acked-by: Alexei Starovoitov 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman