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- an interpreter opened at registration is charged
- an interpreter a 'B' entry binds is charged too
- an entry that opens none is not
- removing an entry gives the charge back
- a nested user namespace cannot buy itself budget by raising its own limit
Skips where the sysctl or binfmt_misc is missing. The 'B' case lives in
binfmt_misc_bpf.c because binding needs a handler. It binds from a child
in a user namespace of its own, through the fd the child inherited, so
the charge lands on the child while the interpreter is still opened with
the entry file's credentials, and nothing outside the child sees a
changed limit.
Link: https://patch.msgid.link/20260803-work-binfmt_misc-interplimit-v1-2-4a2435500bd9@kernel.org
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
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Exercise the 'L' flag end to end. The payload runs as the main image
with a copy of the system loader substituted for its PT_INTERP, and
asserts the native identity from inside:
- argv exactly as the caller built it
- no AT_EXECFD
- AT_FLAGS clear
- AT_BASE set but outside its own image
- AT_PHDR/AT_ENTRY inside it
- /proc/self/{exe,comm,stat} and AT_EXECFN all describing the binary
- ETXTBSY on the running binary
- the substituted loader visible in /proc/self/maps under its real path
Magic matching pokes a marker into the ELF header's e_ident padding
(EI_PAD, offset 9), which sits inside the match window and is ignored by
kernel and loader alike. the same binary is also matched by extension.
Two cases cover the paths where the substitution does not happen. A '#!'
file that matched an 'L' entry is claimed by binfmt_script rather than by
binfmt_elf, so the staged substitute has to be released when the
interpreter replaces the file; the test opens the loader for writing
afterwards, which fails with ETXTBSY if the write denial was leaked
instead. A relative interpreter path is rejected at registration for both
'L' and 'C', neither of which may resolve one against the working
directory of whoever runs the binary.
The bpf-side BPF_BINPRM_LOADER path shares all machinery past the flag
mapping. A harness case for it can join the bpf runtime coverage of
the transparent series.
Link: https://patch.msgid.link/20260721-work-bpf-binfmt_misc-ptinterp-v2-20-e57866e4ae0f@kernel.org
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
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Verify the identity a transparent dispatch constructs, from both
activation paths.
- binfmt_misc_transparent: registers a magic entry with the static 'T'
flag and execs a matched binary with arguments.
- binfmt_misc_bpf: a handler whose load program sets
BPF_BINPRM_TRANSPARENT.
Both dispatch to a shared asserting interpreter that runs in place of
the binary and checks the contract from the inside:
- AT_FLAGS carries AT_FLAGS_TRANSPARENT_INTERP
- AT_EXECFD refers to the very inode of the binary
- /proc/self/exe resolves to the binary
- argv and /proc/self/cmdline are exactly what the caller passed with
nothing spliced in
- comm is the binary's basename
- the binary is write-denied while it runs
The static test also validates the registration. 'T' combined with 'P'
must be rejected. A kernel that does not know 'T' turns the test into a
skip. The asserting interpreter and the static test build without the
bpf toolchain so the core transparent semantics stay covered on systems
where the bpf cases are skipped.
The flag support probe, the canonical payload argv with the
run_payload() helper that execs it, and the identity assertions (exe
link, comm, write denial) live in binfmt_misc_common.h; the loader
substitution test reuses all of them.
Link: https://patch.msgid.link/20260721-work-bpf-binfmt_misc-ptinterp-v2-13-e57866e4ae0f@kernel.org
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
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Exercise the bpf-backed ('B') binfmt_misc handlers end to end. A handler
is a struct binfmt_misc_ops struct_ops map; the test loads and attaches
it (which publishes it by name), activates it with a 'B' entry, and
checks that a matched binary is routed to the interpreter the program
selected via bpf_binprm_set_interp().
Two self-contained cases are covered:
- bpf_interp: the match program matches a synthetic aarch64 ELF header
from the prefetched bprm->buf and the load program routes it to a
fixed interpreter of its choosing.
- nix_origin: the match program parses the program headers to commit
only to a "$ORIGIN/..."-relative PT_INTERP and the load program
resolves it to an interpreter co-located with the binary -- the
relocatable-loader case the kernel ELF loader cannot express. The
relocatable binary is linked with PT_INTERP set to the literal
"$ORIGIN/binfmt_bpf_interp" (-Wl,--dynamic-linker), which the kernel
cannot resolve on its own.
Both route to a small test interpreter that prints a marker, proving the
program-selected interpreter actually ran.
The bpf objects are compiled against the running kernel's BTF: the
Makefile generates vmlinux.h with bpftool and the harness links libbpf.
Override CLANG/BPFTOOL/VMLINUX_BTF/LIBBPF_CFLAGS/LIBBPF_LDLIBS as needed.
The bpf pieces are only built when clang, bpftool, the vmlinux BTF and
libbpf are all present (HAVE_BPF_TOOLCHAIN=y forces them) so the other
exec selftests keep building without a bpf toolchain.
Christian Brauner (Amutable) <brauner@kernel.org> says:
Adapted to the two-op contract: 'B' entries carry the handler name in
the interpreter field, both programs are sleepable, the match programs
decide. nix_origin reads PT_INTERP from the match program and load
returns zero on success. Skip on kernels without binfmt_misc_ops in BTF.
Build the bpf pieces only when the toolchain is present and gitignore
the generated artifacts.
Signed-off-by: Farid Zakaria <farid.m.zakaria@gmail.com>
Link: https://patch.msgid.link/20260714-work-bpf-binfmt_misc-v2-9-57b7529c002c@kernel.org
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
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Add a very simple script interpreter called "inc" that can evaluate two
different commands (one per line):
- "?" to initialize a counter from user's input;
- "+" to increment the counter (which is set to 0 by default).
It is enlighten to only interpret executable files according to
AT_EXECVE_CHECK and the related securebits:
# Executing a script with RESTRICT_FILE is only allowed if the script
# is executable:
./set-exec -f -- ./inc script-exec.inc # Allowed
./set-exec -f -- ./inc script-noexec.inc # Denied
# Executing stdin with DENY_INTERACTIVE is only allowed if stdin is an
# executable regular file:
./set-exec -i -- ./inc -i < script-exec.inc # Allowed
./set-exec -i -- ./inc -i < script-noexec.inc # Denied
# However, a pipe is not executable and it is then denied:
cat script-noexec.inc | ./set-exec -i -- ./inc -i # Denied
# Executing raw data (e.g. command argument) with DENY_INTERACTIVE is
# always denied.
./set-exec -i -- ./inc -c "+" # Denied
./inc -c "$(<script-ask.inc)" # Allowed
# To directly execute a script, we can update $PATH (used by `env`):
PATH="${PATH}:." ./script-exec.inc
# To execute several commands passed as argument:
Add a complete test suite to check the script interpreter against all
possible execution cases:
make TARGETS=exec kselftest-install
./tools/testing/selftests/kselftest_install/run_kselftest.sh
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Paul Moore <paul@paul-moore.com>
Cc: Serge Hallyn <serge@hallyn.com>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Link: https://lore.kernel.org/r/20241212174223.389435-8-mic@digikod.net
Signed-off-by: Kees Cook <kees@kernel.org>
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Test that checks performed by execveat(..., AT_EXECVE_CHECK) are
consistent with noexec mount points and file execute permissions.
Test that SECBIT_EXEC_RESTRICT_FILE and SECBIT_EXEC_DENY_INTERACTIVE are
inherited by child processes and that they can be pinned with the
appropriate SECBIT_EXEC_RESTRICT_FILE_LOCKED and
SECBIT_EXEC_DENY_INTERACTIVE_LOCKED bits.
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Paul Moore <paul@paul-moore.com>
Cc: Serge Hallyn <serge@hallyn.com>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Link: https://lore.kernel.org/r/20241212174223.389435-4-mic@digikod.net
Signed-off-by: Kees Cook <kees@kernel.org>
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The name of the "load_address" objects has been modified, but the
corresponding entry in the gitignore file must be updated.
Update the load_address entry in the gitignore file to account for
the new names, adding an exception to keep on tracking load_address.c.
Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
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Add generated files non-regular and null-argv to .gitignore file.
Signed-off-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
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This produces a PIE binary with a variety of p_align requirements,
suitable for verifying that the load address meets that alignment
requirement.
Signed-off-by: Chris Kennelly <ckennelly@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Fangrui Song <maskray@google.com>
Cc: Hugh Dickens <hughd@google.com>
Cc: Ian Rogers <irogers@google.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Sandeep Patil <sspatil@google.com>
Cc: Song Liu <songliubraving@fb.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Link: https://lkml.kernel.org/r/20200820170541.1132271-3-ckennelly@google.com
Link: https://lkml.kernel.org/r/20200821233848.3904680-3-ckennelly@google.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Make sure execve() returns the expected errno values for non-regular
files.
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Marc Zyngier <maz@kernel.org>
Link: http://lkml.kernel.org/r/20200813231723.2725102-3-keescook@chromium.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Add a named pipe as an exec target to make sure that non-regular
files are rejected by execve() with EACCES. This can help verify
commit 73601ea5b7b1 ("fs/open.c: allow opening only regular files
during execve()").
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
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Add SPDX License Identifier to all .gitignore files.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Test that trivially recursing script onto itself doesn't work.
Note: this is different test from ELOOP tests in execveat.c Those test
that execveat(2) doesn't follow symlinks when told to do so.
Link: http://lkml.kernel.org/r/20190423192720.GA21433@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Signed-off-by: David Drysdale <drysdale@google.com>
Cc: Meredydd Luff <meredydd@senatehouse.org>
Cc: Shuah Khan <shuah.kh@samsung.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Rich Felker <dalias@aerifal.cx>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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