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Quentin Monnet a230cd3051 libbpf: Fix segfault due to libelf functions not setting errno 
[ Upstream commit e10500b69c ]

Libelf functions do not set errno on failure. Instead, it relies on its
internal _elf_errno value, that can be retrieved via elf_errno (or the
corresponding message via elf_errmsg()). From "man libelf":

    If a libelf function encounters an error it will set an internal
    error code that can be retrieved with elf_errno. Each thread
    maintains its own separate error code. The meaning of each error
    code can be determined with elf_errmsg, which returns a string
    describing the error.

As a consequence, libbpf should not return -errno when a function from
libelf fails, because an empty value will not be interpreted as an error
and won't prevent the program to stop. This is visible in
bpf_linker__add_file(), for example, where we call a succession of
functions that rely on libelf:

    err = err ?: linker_load_obj_file(linker, filename, opts, &obj);
    err = err ?: linker_append_sec_data(linker, &obj);
    err = err ?: linker_append_elf_syms(linker, &obj);
    err = err ?: linker_append_elf_relos(linker, &obj);
    err = err ?: linker_append_btf(linker, &obj);
    err = err ?: linker_append_btf_ext(linker, &obj);

If the object file that we try to process is not, in fact, a correct
object file, linker_load_obj_file() may fail with errno not being set,
and return 0. In this case we attempt to run linker_append_elf_sysms()
and may segfault.

This can happen (and was discovered) with bpftool:

    $ bpftool gen object output.o sample_ret0.bpf.c
    libbpf: failed to get ELF header for sample_ret0.bpf.c: invalid `Elf' handle
    zsh: segmentation fault (core dumped)  bpftool gen object output.o sample_ret0.bpf.c

Fix the issue by returning a non-null error code (-EINVAL) when libelf
functions fail.

Fixes: faf6ed321c ("libbpf: Add BPF static linker APIs")
Signed-off-by: Quentin Monnet <qmo@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20241205135942.65262-1-qmo@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2025-02-08 09:57:27 +01:00
arch arm64: dts: imx93: Use IMX93_CLK_SPDIF_IPG as SPDIF IPG clock 2025-02-08 09:57:09 +01:00
block partitions: ldm: remove the initial kernel-doc notation 2025-02-08 09:56:52 +01:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: ecdsa - Avoid signed integer overflow on signature decoding 2024-12-14 20:03:36 +01:00
Documentation dt-bindings: clock: Add i.MX91 clock support 2025-02-08 09:57:08 +01:00
drivers pinctrl: samsung: Fix irq handling if an error occurs in exynos_irq_demux_eint16_31() 2025-02-08 09:57:26 +01:00
fs afs: Fix the fallback handling for the YFS.RemoveFile2 RPC call 2025-02-08 09:56:53 +01:00
include net: sched: refine software bypass handling in tc_run 2025-02-08 09:57:25 +01:00
init Compiler Attributes: disable __counted_by for clang < 19.1.3 2024-12-05 14:02:45 +01:00
io_uring io_uring/rsrc: require cloned buffers to share accounting contexts 2025-02-01 18:39:40 +01:00
ipc ipc: fix memleak if msg_init_ns failed in create_ipc_ns 2024-12-05 14:03:02 +01:00
kernel cpufreq: schedutil: Fix superfluous updates caused by need_freq_update 2025-02-08 09:57:06 +01:00
lib maple_tree: reload mas before the second call for mas_empty_area 2025-01-09 13:33:50 +01:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm cachestat: fix page cache statistics permission checking 2025-02-01 18:39:38 +01:00
net net/rose: prevent integer overflows in rose_setsockopt() 2025-02-08 09:57:25 +01:00
rust rust: kbuild: set bindgen's Rust target version 2024-12-19 18:13:22 +01:00
samples samples/landlock: Fix possible NULL dereference in parse_path() 2025-02-08 09:57:11 +01:00
scripts scripts/sorttable: fix orc_sort_cmp() to maintain symmetry and transitivity 2025-01-09 13:33:50 +01:00
security landlock: Handle weird files 2025-02-08 09:57:16 +01:00
sound ASoC: wcd937x: Use *-y for Makefile 2025-02-08 09:57:26 +01:00
tools libbpf: Fix segfault due to libelf functions not setting errno 2025-02-08 09:57:27 +01:00
usr initramfs: shorten cmd_initfs in usr/Makefile 2024-07-16 01:07:52 +09:00
virt KVM: x86: switch hugepage recovery thread to vhost_task 2024-12-05 14:02:43 +01:00
.clang-format clang-format: Update with v6.11-rc1's for_each macro list 2024-08-02 13:20:31 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore Kbuild updates for v6.12 2024-09-24 13:02:06 -07:00
.mailmap mailmap: add entry for Thorsten Blum 2024-11-07 14:14:59 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Remove self from DSA entry 2024-11-03 12:52:38 -08:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS MAINTAINERS: update location of media main tree 2024-12-05 14:02:42 +01:00
Makefile Linux 6.12.12 2025-02-01 18:39:40 +01:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.