linux-toradex.git/kernel/bpf, branch v5.7-rc5

bpf: Make bpf_link_fops static

2020-04-25T00:42:44+00:00

Fix the following sparse warning:

kernel/bpf/syscall.c:2289:30: warning: symbol 'bpf_link_fops' was not declared. Should it be static?

Reported-by: Hulk Robot 
Signed-off-by: Zou Wei 
Signed-off-by: Alexei Starovoitov 
Acked-by: Andrii Nakryiko 
Link: https://lore.kernel.org/bpf/1587609160-117806-1-git-send-email-zou_wei@huawei.com

bpf: Propagate expected_attach_type when verifying freplace programs

2020-04-25T00:34:30+00:00

For some program types, the verifier relies on the expected_attach_type of
the program being verified in the verification process. However, for
freplace programs, the attach type was not propagated along with the
verifier ops, so the expected_attach_type would always be zero for freplace
programs.

This in turn caused the verifier to sometimes make the wrong call for
freplace programs. For all existing uses of expected_attach_type for this
purpose, the result of this was only false negatives (i.e., freplace
functions would be rejected by the verifier even though they were valid
programs for the target they were replacing). However, should a false
positive be introduced, this can lead to out-of-bounds accesses and/or
crashes.

The fix introduced in this patch is to propagate the expected_attach_type
to the freplace program during verification, and reset it after that is
done.

Fixes: be8704ff07d2 ("bpf: Introduce dynamic program extensions")
Signed-off-by: Toke Høiland-Jørgensen 
Signed-off-by: Alexei Starovoitov 
Link: https://lore.kernel.org/bpf/158773526726.293902.13257293296560360508.stgit@toke.dk

bpf: Fix leak in LINK_UPDATE and enforce empty old_prog_fd

2020-04-25T00:27:02+00:00

Fix bug of not putting bpf_link in LINK_UPDATE command.
Also enforce zeroed old_prog_fd if no BPF_F_REPLACE flag is specified.

Signed-off-by: Andrii Nakryiko 
Signed-off-by: Alexei Starovoitov 
Link: https://lore.kernel.org/bpf/20200424052045.4002963-1-andriin@fb.com

bpf: Fix handling of XADD on BTF memory

2020-04-21T01:41:34+00:00

check_xadd() can cause check_ptr_to_btf_access() to be executed with
atype==BPF_READ and value_regno==-1 (meaning "just check whether the access
is okay, don't tell me what type it will result in").
Handle that case properly and skip writing type information, instead of
indexing into the registers at index -1 and writing into out-of-bounds
memory.

Note that at least at the moment, you can't actually write through a BTF
pointer, so check_xadd() will reject the program after calling
check_ptr_to_btf_access with atype==BPF_WRITE; but that's after the
verifier has already corrupted memory.

This patch assumes that BTF pointers are not available in unprivileged
programs.

Fixes: 9e15db66136a ("bpf: Implement accurate raw_tp context access via BTF")
Signed-off-by: Jann Horn 
Signed-off-by: Alexei Starovoitov 
Link: https://lore.kernel.org/bpf/20200417000007.10734-2-jannh@google.com

bpf: Forbid XADD on spilled pointers for unprivileged users

2020-04-21T01:41:34+00:00

When check_xadd() verifies an XADD operation on a pointer to a stack slot
containing a spilled pointer, check_stack_read() verifies that the read,
which is part of XADD, is valid. However, since the placeholder value -1 is
passed as `value_regno`, check_stack_read() can only return a binary
decision and can't return the type of the value that was read. The intent
here is to verify whether the value read from the stack slot may be used as
a SCALAR_VALUE; but since check_stack_read() doesn't check the type, and
the type information is lost when check_stack_read() returns, this is not
enforced, and a malicious user can abuse XADD to leak spilled kernel
pointers.

Fix it by letting check_stack_read() verify that the value is usable as a
SCALAR_VALUE if no type information is passed to the caller.

To be able to use __is_pointer_value() in check_stack_read(), move it up.

Fix up the expected unprivileged error message for a BPF selftest that,
until now, assumed that unprivileged users can use XADD on stack-spilled
pointers. This also gives us a test for the behavior introduced in this
patch for free.

In theory, this could also be fixed by forbidding XADD on stack spills
entirely, since XADD is a locked operation (for operations on memory with
concurrency) and there can't be any concurrency on the BPF stack; but
Alexei has said that he wants to keep XADD on stack slots working to avoid
changes to the test suite [1].

The following BPF program demonstrates how to leak a BPF map pointer as an
unprivileged user using this bug:

    // r7 = map_pointer
    BPF_LD_MAP_FD(BPF_REG_7, small_map),
    // r8 = launder(map_pointer)
    BPF_STX_MEM(BPF_DW, BPF_REG_FP, BPF_REG_7, -8),
    BPF_MOV64_IMM(BPF_REG_1, 0),
    ((struct bpf_insn) {
      .code  = BPF_STX | BPF_DW | BPF_XADD,
      .dst_reg = BPF_REG_FP,
      .src_reg = BPF_REG_1,
      .off = -8
    }),
    BPF_LDX_MEM(BPF_DW, BPF_REG_8, BPF_REG_FP, -8),

    // store r8 into map
    BPF_MOV64_REG(BPF_REG_ARG1, BPF_REG_7),
    BPF_MOV64_REG(BPF_REG_ARG2, BPF_REG_FP),
    BPF_ALU64_IMM(BPF_ADD, BPF_REG_ARG2, -4),
    BPF_ST_MEM(BPF_W, BPF_REG_ARG2, 0, 0),
    BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
    BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 1),
    BPF_EXIT_INSN(),
    BPF_STX_MEM(BPF_DW, BPF_REG_0, BPF_REG_8, 0),

    BPF_MOV64_IMM(BPF_REG_0, 0),
    BPF_EXIT_INSN()

[1] https://lore.kernel.org/bpf/20200416211116.qxqcza5vo2ddnkdq@ast-mbp.dhcp.thefacebook.com/

Fixes: 17a5267067f3 ("bpf: verifier (add verifier core)")
Signed-off-by: Jann Horn 
Signed-off-by: Alexei Starovoitov 
Link: https://lore.kernel.org/bpf/20200417000007.10734-1-jannh@google.com

cpumap: Avoid warning when CONFIG_DEBUG_PER_CPU_MAPS is enabled

2020-04-21T01:38:04+00:00

When the kernel is built with CONFIG_DEBUG_PER_CPU_MAPS, the cpumap code
can trigger a spurious warning if CONFIG_CPUMASK_OFFSTACK is also set. This
happens because in this configuration, NR_CPUS can be larger than
nr_cpumask_bits, so the initial check in cpu_map_alloc() is not sufficient
to guard against hitting the warning in cpumask_check().

Fix this by explicitly checking the supplied key against the
nr_cpumask_bits variable before calling cpu_possible().

Fixes: 6710e1126934 ("bpf: introduce new bpf cpu map type BPF_MAP_TYPE_CPUMAP")
Reported-by: Xiumei Mu 
Signed-off-by: Toke Høiland-Jørgensen 
Signed-off-by: Alexei Starovoitov 
Tested-by: Xiumei Mu 
Acked-by: Jesper Dangaard Brouer 
Acked-by: Song Liu 
Link: https://lore.kernel.org/bpf/20200416083120.453718-1-toke@redhat.com

bpf: remove unneeded conversion to bool in __mark_reg_unknown

2020-04-14T19:40:06+00:00

This issue was detected by using the Coccinelle software:

  kernel/bpf/verifier.c:1259:16-21: WARNING: conversion to bool not needed here

The conversion to bool is unneeded, remove it.

Reported-by: Hulk Robot 
Signed-off-by: Zou Wei 
Signed-off-by: Daniel Borkmann 
Acked-by: Song Liu 
Link: https://lore.kernel.org/bpf/1586779076-101346-1-git-send-email-zou_wei@huawei.com

bpf: Prevent re-mmap()'ing BPF map as writable for initially r/o mapping

2020-04-14T19:28:57+00:00

VM_MAYWRITE flag during initial memory mapping determines if already mmap()'ed
pages can be later remapped as writable ones through mprotect() call. To
prevent user application to rewrite contents of memory-mapped as read-only and
subsequently frozen BPF map, remove VM_MAYWRITE flag completely on initially
read-only mapping.

Alternatively, we could treat any memory-mapping on unfrozen map as writable
and bump writecnt instead. But there is little legitimate reason to map
BPF map as read-only and then re-mmap() it as writable through mprotect(),
instead of just mmap()'ing it as read/write from the very beginning.

Also, at the suggestion of Jann Horn, drop unnecessary refcounting in mmap
operations. We can just rely on VMA holding reference to BPF map's file
properly.

Fixes: fc9702273e2e ("bpf: Add mmap() support for BPF_MAP_TYPE_ARRAY")
Reported-by: Jann Horn 
Signed-off-by: Andrii Nakryiko 
Signed-off-by: Daniel Borkmann 
Reviewed-by: Jann Horn 
Link: https://lore.kernel.org/bpf/20200410202613.3679837-1-andriin@fb.com

bpf: Fix a typo "inacitve" -> "inactive"

2020-04-06T19:54:10+00:00

There is a typo in struct bpf_lru_list's next_inactive_rotation
description, thus fix s/inacitve/inactive/.

Signed-off-by: Qiujun Huang 
Signed-off-by: Daniel Borkmann 
Link: https://lore.kernel.org/bpf/1585901254-30377-1-git-send-email-hqjagain@gmail.com

Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next

2020-03-31T02:52:37+00:00

Signed-off-by: David S. Miller