linux-stable.git/kernel/bpf/btf.c, branch v6.11.2

bpf: correctly handle malformed BPF_CORE_TYPE_ID_LOCAL relos

2024-10-04T14:37:58+00:00

[ Upstream commit 3d2786d65aaa954ebd3fcc033ada433e10da21c4 ]

In case of malformed relocation record of kind BPF_CORE_TYPE_ID_LOCAL
referencing a non-existing BTF type, function bpf_core_calc_relo_insn
would cause a null pointer deference.

Fix this by adding a proper check upper in call stack, as malformed
relocation records could be passed from user space.

Simplest reproducer is a program:

    r0 = 0
    exit

With a single relocation record:

    .insn_off = 0,          /* patch first instruction */
    .type_id = 100500,      /* this type id does not exist */
    .access_str_off = 6,    /* offset of string "0" */
    .kind = BPF_CORE_TYPE_ID_LOCAL,

See the link for original reproducer or next commit for a test case.

Fixes: 74753e1462e7 ("libbpf: Replace btf__type_by_id() with btf_type_by_id().")
Reported-by: Liu RuiTong 
Closes: https://lore.kernel.org/bpf/CAK55_s6do7C+DVwbwY_7nKfUz0YLDoiA1v6X3Y9+p0sWzipFSA@mail.gmail.com/
Acked-by: Andrii Nakryiko 
Signed-off-by: Eduard Zingerman 
Link: https://lore.kernel.org/r/20240822080124.2995724-2-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov 
Signed-off-by: Sasha Levin

bpf, lsm: Add check for BPF LSM return value

2024-10-04T14:37:52+00:00

[ Upstream commit 5d99e198be279045e6ecefe220f5c52f8ce9bfd5 ]

A bpf prog returning a positive number attached to file_alloc_security
hook makes kernel panic.

This happens because file system can not filter out the positive number
returned by the LSM prog using IS_ERR, and misinterprets this positive
number as a file pointer.

Given that hook file_alloc_security never returned positive number
before the introduction of BPF LSM, and other BPF LSM hooks may
encounter similar issues, this patch adds LSM return value check
in verifier, to ensure no unexpected value is returned.

Fixes: 520b7aa00d8c ("bpf: lsm: Initialize the BPF LSM hooks")
Reported-by: Xin Liu 
Signed-off-by: Xu Kuohai 
Acked-by: Eduard Zingerman 
Link: https://lore.kernel.org/r/20240719110059.797546-3-xukuohai@huaweicloud.com
Signed-off-by: Alexei Starovoitov 
Signed-off-by: Andrii Nakryiko 
Signed-off-by: Sasha Levin

bpf: add check for invalid name in btf_name_valid_section()

2024-09-04T18:56:34+00:00

If the length of the name string is 1 and the value of name[0] is NULL
byte, an OOB vulnerability occurs in btf_name_valid_section() and the
return value is true, so the invalid name passes the check.

To solve this, you need to check if the first position is NULL byte and
if the first character is printable.

Suggested-by: Eduard Zingerman 
Fixes: bd70a8fb7ca4 ("bpf: Allow all printable characters in BTF DATASEC names")
Signed-off-by: Jeongjun Park 
Link: https://lore.kernel.org/r/20240831054702.364455-1-aha310510@gmail.com
Signed-off-by: Alexei Starovoitov 
Acked-by: Eduard Zingerman

bpf: Fix a crash when btf_parse_base() returns an error pointer

2024-08-30T17:34:47+00:00

The pointer returned by btf_parse_base could be an error pointer.
IS_ERR() check is needed before calling btf_free(base_btf).

Fixes: 8646db238997 ("libbpf,bpf: Share BTF relocate-related code with kernel")
Signed-off-by: Martin KaFai Lau 
Signed-off-by: Andrii Nakryiko 
Reviewed-by: Alan Maguire 
Acked-by: Eduard Zingerman 
Link: https://lore.kernel.org/bpf/20240830012214.1646005-1-martin.lau@linux.dev

bpf: Eliminate remaining "make W=1" warnings in kernel/bpf/btf.o

2024-07-12T15:02:26+00:00

As reported by Mirsad [1] we still see format warnings in kernel/bpf/btf.o
at W=1 warning level:

  CC      kernel/bpf/btf.o
./kernel/bpf/btf.c: In function ‘btf_type_seq_show_flags’:
./kernel/bpf/btf.c:7553:21: warning: assignment left-hand side might be a candidate for a format attribute [-Wsuggest-attribute=format]
 7553 |         sseq.showfn = btf_seq_show;
      |                     ^
./kernel/bpf/btf.c: In function ‘btf_type_snprintf_show’:
./kernel/bpf/btf.c:7604:31: warning: assignment left-hand side might be a candidate for a format attribute [-Wsuggest-attribute=format]
 7604 |         ssnprintf.show.showfn = btf_snprintf_show;
      |                               ^

Combined with CONFIG_WERROR=y these can halt the build.

The fix (annotating the structure field with __printf())
suggested by Mirsad resolves these. Apologies I missed this last time.
No other W=1 warnings were observed in kernel/bpf after this fix.

[1] https://lore.kernel.org/bpf/92c9d047-f058-400c-9c7d-81d4dc1ef71b@gmail.com/

Fixes: b3470da314fd ("bpf: annotate BTF show functions with __printf")
Reported-by: Mirsad Todorovac 
Suggested-by: Mirsad Todorovac 
Signed-off-by: Alan Maguire 
Signed-off-by: Daniel Borkmann 
Link: https://lore.kernel.org/bpf/20240712092859.1390960-1-alan.maguire@oracle.com

bpf: annotate BTF show functions with __printf

2024-07-11T21:15:17+00:00

-Werror=suggest-attribute=format warns about two functions
in kernel/bpf/btf.c [1]; add __printf() annotations to silence
these warnings since for CONFIG_WERROR=y they will trigger
build failures.

[1] https://lore.kernel.org/bpf/a8b20c72-6631-4404-9e1f-0410642d7d20@gmail.com/

Fixes: 31d0bc81637d ("bpf: Move to generic BTF show support, apply it to seq files/strings")
Reported-by: Mirsad Todorovac 
Signed-off-by: Alan Maguire 
Tested-by: Mirsad Todorovac 
Link: https://lore.kernel.org/r/20240711182321.963667-1-alan.maguire@oracle.com
Signed-off-by: Alexei Starovoitov

bpf: fix build when CONFIG_DEBUG_INFO_BTF[_MODULES] is undefined

2024-06-23T19:50:02+00:00

Kernel test robot reports that kernel build fails with
resilient split BTF changes.

Examining the associated config and code we see that
btf_relocate_id() is defined under CONFIG_DEBUG_INFO_BTF_MODULES.
Moving it outside the #ifdef solves the issue.

Reported-by: kernel test robot 
Closes: https://lore.kernel.org/oe-kbuild-all/202406221742.d2srFLVI-lkp@intel.com/
Signed-off-by: Alan Maguire 
Link: https://lore.kernel.org/r/20240623135224.27981-1-alan.maguire@oracle.com
Signed-off-by: Alexei Starovoitov

libbpf,bpf: Share BTF relocate-related code with kernel

2024-06-21T21:45:07+00:00

Share relocation implementation with the kernel.  As part of this,
we also need the type/string iteration functions so also share
btf_iter.c file. Relocation code in kernel and userspace is identical
save for the impementation of the reparenting of split BTF to the
relocated base BTF and retrieval of the BTF header from "struct btf";
these small functions need separate user-space and kernel implementations
for the separate "struct btf"s they operate upon.

One other wrinkle on the kernel side is we have to map .BTF.ids in
modules as they were generated with the type ids used at BTF encoding
time. btf_relocate() optionally returns an array mapping from old BTF
ids to relocated ids, so we use that to fix up these references where
needed for kfuncs.

Signed-off-by: Alan Maguire 
Signed-off-by: Andrii Nakryiko 
Acked-by: Eduard Zingerman 
Link: https://lore.kernel.org/bpf/20240620091733.1967885-5-alan.maguire@oracle.com

bpf: verifier: Relax caller requirements for kfunc projection type args

2024-06-12T18:01:31+00:00

Currently, if a kfunc accepts a projection type as an argument (eg
struct __sk_buff *), the caller must exactly provide exactly the same
type with provable provenance.

However in practice, kfuncs that accept projection types _must_ cast to
the underlying type before use b/c projection type layouts are
completely made up. Thus, it is ok to relax the verifier rules around
implicit conversions.

We will use this functionality in the next commit when we align kfuncs
to user-facing types.

Signed-off-by: Daniel Xu 
Link: https://lore.kernel.org/r/e2c025cb09ccfd4af1ec9e18284dc3cecff7514d.1718207789.git.dxu@dxuuu.xyz
Signed-off-by: Alexei Starovoitov

bpf: limit the number of levels of a nested struct type.

2024-06-04T03:52:42+00:00

Limit the number of levels looking into struct types to avoid running out
of stack space.

Acked-by: Eduard Zingerman 
Signed-off-by: Kui-Feng Lee 
Link: https://lore.kernel.org/r/20240523174202.461236-7-thinker.li@gmail.com
Signed-off-by: Alexei Starovoitov