From: Christian Brauner <brauner@kernel.org>
To: Farid Zakaria <farid.m.zakaria@gmail.com>,
linux-fsdevel@vger.kernel.org
Cc: Daniel Borkmann <daniel@iogearbox.net>,
Alexei Starovoitov <ast@kernel.org>, Kees Cook <kees@kernel.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Jan Kara <jack@suse.cz>, Jonathan Corbet <corbet@lwn.net>,
linux-mm@kvack.org, bpf@vger.kernel.org, jannh@google.com,
mail@johnericson.me,
"Christian Brauner (Amutable)" <brauner@kernel.org>
Subject: [PATCH 06/21] binfmt_misc: split out build_interp_argv()
Date: Mon, 20 Jul 2026 11:33:29 +0200 [thread overview]
Message-ID: <20260720-work-bpf-binfmt_misc-ptinterp-v1-6-ddb76c9a508e@kernel.org> (raw)
In-Reply-To: <20260720-work-bpf-binfmt_misc-ptinterp-v1-0-ddb76c9a508e@kernel.org>
Building the interpreter's argument vector is the bulk of
load_misc_binary() and the one part of it that is specific to the
classic dispatch. Move it into its own helper so what remains reads as
what it is: pick a handler, pick an interpreter, build the invocation,
open it.
No functional change.
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
---
fs/binfmt_misc.c | 84 ++++++++++++++++++++++++++++++++++++--------------------
1 file changed, 54 insertions(+), 30 deletions(-)
diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c
index 63c10066e3a6..f0ccc5d000f6 100644
--- a/fs/binfmt_misc.c
+++ b/fs/binfmt_misc.c
@@ -382,40 +382,23 @@ static struct file *entry_open_interpreter(const struct binfmt_misc_entry *e,
return no_free_ptr(interp_file);
}
-/*
- * the loader itself
+/**
+ * build_interp_argv - splice the interpreter invocation into the argv
+ * @bprm: binary that is being executed
+ * @interpreter: the interpreter selected for this exec
+ * @flags: invocation flags in effect for this exec
+ *
+ * The interpreter becomes argv[0] and the binary its last argument, with an
+ * optional staged argument in between. The caller's argv[0] is dropped
+ * unless 'P' keeps it.
+ *
+ * Return: 0 on success, a negative error code on failure
*/
-static int load_misc_binary(struct linux_binprm *bprm)
+static int build_interp_argv(struct linux_binprm *bprm, const char *interpreter,
+ unsigned long flags)
{
- struct binfmt_misc_entry *fmt __free(put_binfmt_handler) = NULL;
- const char *interpreter;
- struct file *interp_file;
- struct binfmt_misc *misc;
- unsigned long flags;
int retval;
- misc = current_binfmt_misc();
- if (!READ_ONCE(misc->enabled))
- return -ENOEXEC;
-
- fmt = get_binfmt_handler(misc, bprm);
- if (!fmt)
- return -ENOEXEC;
-
- /* Need to be able to load the file after exec */
- if (bprm->interp_flags & BINPRM_FLAGS_PATH_INACCESSIBLE)
- return -ENOENT;
-
- interpreter = entry_select_interpreter(fmt, bprm);
- if (IS_ERR(interpreter))
- return PTR_ERR(interpreter);
-
- flags = entry_invocation_flags(fmt, bprm);
- if (flags & MISC_FMT_CREDENTIALS)
- bprm->execfd_creds = 1;
- if (flags & MISC_FMT_OPEN_BINARY)
- bprm->have_execfd = 1;
-
/* The entry's own choice - not one accumulated from an earlier level. */
if (flags & MISC_FMT_PRESERVE_ARGV0) {
bprm->interp_flags |= BINPRM_FLAGS_PRESERVE_ARGV0;
@@ -451,6 +434,47 @@ static int load_misc_binary(struct linux_binprm *bprm)
return retval;
bprm->argc++;
+ return 0;
+}
+
+/*
+ * the loader itself
+ */
+static int load_misc_binary(struct linux_binprm *bprm)
+{
+ struct binfmt_misc_entry *fmt __free(put_binfmt_handler) = NULL;
+ const char *interpreter;
+ struct file *interp_file;
+ struct binfmt_misc *misc;
+ unsigned long flags;
+ int retval;
+
+ misc = current_binfmt_misc();
+ if (!READ_ONCE(misc->enabled))
+ return -ENOEXEC;
+
+ fmt = get_binfmt_handler(misc, bprm);
+ if (!fmt)
+ return -ENOEXEC;
+
+ /* Need to be able to load the file after exec */
+ if (bprm->interp_flags & BINPRM_FLAGS_PATH_INACCESSIBLE)
+ return -ENOENT;
+
+ interpreter = entry_select_interpreter(fmt, bprm);
+ if (IS_ERR(interpreter))
+ return PTR_ERR(interpreter);
+
+ flags = entry_invocation_flags(fmt, bprm);
+ if (flags & MISC_FMT_CREDENTIALS)
+ bprm->execfd_creds = 1;
+ if (flags & MISC_FMT_OPEN_BINARY)
+ bprm->have_execfd = 1;
+
+ retval = build_interp_argv(bprm, interpreter, flags);
+ if (retval)
+ return retval;
+
/* Update interp in case binfmt_script needs it. */
retval = bprm_change_interp(interpreter, bprm);
if (retval < 0)
--
2.53.0
next prev parent reply other threads:[~2026-07-20 9:34 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-20 9:33 [PATCH 00/21] binfmt_misc: transparent interpreters and PT_INTERP loader substitution Christian Brauner
2026-07-20 9:33 ` [PATCH 01/21] exec: do not act on a stale execfd request without an executable Christian Brauner
2026-07-20 9:33 ` [PATCH 02/21] docs, binfmt_misc: keep general usage out of the handler sections Christian Brauner
2026-07-20 9:33 ` [PATCH 03/21] binfmt_misc: table-drive the register string flags Christian Brauner
2026-07-20 9:33 ` [PATCH 04/21] binfmt_misc: normalize the per-exec invocation flags Christian Brauner
2026-07-20 9:33 ` [PATCH 05/21] binfmt_misc: split out entry_open_interpreter() Christian Brauner
2026-07-20 9:33 ` Christian Brauner [this message]
2026-07-20 9:33 ` [PATCH 07/21] exec: release the replaced file with do_close_execat() Christian Brauner
2026-07-20 9:33 ` [PATCH 08/21] exec: add AT_FLAGS_TRANSPARENT_INTERP Christian Brauner
2026-07-20 9:33 ` [PATCH 09/21] exec: label mm->exe_file with the binary for a transparent dispatch Christian Brauner
2026-07-20 9:33 ` [PATCH 10/21] binfmt_misc: add transparent interpreter dispatch Christian Brauner
2026-07-20 9:33 ` [PATCH 11/21] binfmt_misc: add a static transparent flag 'T' Christian Brauner
2026-07-20 9:33 ` [PATCH 12/21] binfmt_misc: let a bpf handler run the interpreter transparently Christian Brauner
2026-07-20 9:33 ` [PATCH 13/21] selftests/exec: convert the binfmt_misc bpf test to the kselftest harness Christian Brauner
2026-07-20 9:33 ` [PATCH 14/21] selftests/exec: test the transparent binfmt_misc mode Christian Brauner
2026-07-20 9:33 ` [PATCH 15/21] binfmt_misc: document the transparent identity contract Christian Brauner
2026-07-20 9:33 ` [PATCH 16/21] exec: carry a PT_INTERP substitute in struct linux_binprm Christian Brauner
2026-07-20 9:33 ` [PATCH 17/21] binfmt_elf: consume a stashed PT_INTERP substitute Christian Brauner
2026-07-20 9:33 ` [PATCH 18/21] binfmt_misc: add the 'L' loader substitution flag Christian Brauner
2026-07-20 9:33 ` [PATCH 19/21] binfmt_misc: let a bpf handler request loader substitution Christian Brauner
2026-07-20 9:33 ` [PATCH 20/21] selftests/exec: test binfmt_misc " Christian Brauner
2026-07-20 9:33 ` [PATCH 21/21] binfmt_misc: document " Christian Brauner
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