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* + binfmt_elf_fdpic-fix-proc-pid-auxv.patch added to mm-nonmm-unstable branch
@ 2024-04-22 22:01 Andrew Morton
  2024-04-24 22:54 ` Kees Cook
  0 siblings, 1 reply; 2+ messages in thread
From: Andrew Morton @ 2024-04-22 22:01 UTC (permalink / raw)
  To: mm-commits, viro, keescook, jack, ebiederm, brauner, jcmvbkbc,
	akpm


The patch titled
     Subject: binfmt_elf_fdpic: fix /proc/<pid>/auxv
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     binfmt_elf_fdpic-fix-proc-pid-auxv.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/binfmt_elf_fdpic-fix-proc-pid-auxv.patch

This patch will later appear in the mm-nonmm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

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branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days

------------------------------------------------------
From: Max Filippov <jcmvbkbc@gmail.com>
Subject: binfmt_elf_fdpic: fix /proc/<pid>/auxv
Date: Fri, 22 Mar 2024 12:54:18 -0700

Althought FDPIC linux kernel provides /proc/<pid>/auxv files they are
empty because there's no code that initializes mm->saved_auxv in the FDPIC
ELF loader.

Synchronize FDPIC ELF aux vector setup with ELF.  Replace entry-by-entry
aux vector copying to userspace with initialization of mm->saved_auxv
first and then copying it to userspace as a whole.

Link: https://lkml.kernel.org/r/20240322195418.2160164-1-jcmvbkbc@gmail.com
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/binfmt_elf_fdpic.c |   90 +++++++++++++++++++---------------------
 1 file changed, 43 insertions(+), 47 deletions(-)

--- a/fs/binfmt_elf_fdpic.c~binfmt_elf_fdpic-fix-proc-pid-auxv
+++ a/fs/binfmt_elf_fdpic.c
@@ -505,8 +505,9 @@ static int create_elf_fdpic_tables(struc
 	char *k_platform, *k_base_platform;
 	char __user *u_platform, *u_base_platform, *p;
 	int loop;
-	int nr;	/* reset for each csp adjustment */
 	unsigned long flags = 0;
+	int ei_index;
+	elf_addr_t *elf_info;
 
 #ifdef CONFIG_MMU
 	/* In some cases (e.g. Hyper-Threading), we want to avoid L1 evictions
@@ -601,44 +602,24 @@ static int create_elf_fdpic_tables(struc
 	csp -= sp & 15UL;
 	sp -= sp & 15UL;
 
-	/* put the ELF interpreter info on the stack */
-#define NEW_AUX_ENT(id, val)						\
-	do {								\
-		struct { unsigned long _id, _val; } __user *ent, v;	\
-									\
-		ent = (void __user *) csp;				\
-		v._id = (id);						\
-		v._val = (val);						\
-		if (copy_to_user(ent + nr, &v, sizeof(v)))		\
-			return -EFAULT;					\
-		nr++;							\
+	/* Create the ELF interpreter info */
+	elf_info = (elf_addr_t *)mm->saved_auxv;
+	/* update AT_VECTOR_SIZE_BASE if the number of NEW_AUX_ENT() changes */
+#define NEW_AUX_ENT(id, val) \
+	do { \
+		*elf_info++ = id; \
+		*elf_info++ = val; \
 	} while (0)
 
-	nr = 0;
-	csp -= 2 * sizeof(unsigned long);
-	NEW_AUX_ENT(AT_NULL, 0);
-	if (k_platform) {
-		nr = 0;
-		csp -= 2 * sizeof(unsigned long);
-		NEW_AUX_ENT(AT_PLATFORM,
-			    (elf_addr_t) (unsigned long) u_platform);
-	}
-
-	if (k_base_platform) {
-		nr = 0;
-		csp -= 2 * sizeof(unsigned long);
-		NEW_AUX_ENT(AT_BASE_PLATFORM,
-			    (elf_addr_t) (unsigned long) u_base_platform);
-	}
-
-	if (bprm->have_execfd) {
-		nr = 0;
-		csp -= 2 * sizeof(unsigned long);
-		NEW_AUX_ENT(AT_EXECFD, bprm->execfd);
-	}
-
-	nr = 0;
-	csp -= DLINFO_ITEMS * 2 * sizeof(unsigned long);
+#ifdef ARCH_DLINFO
+	/*
+	 * ARCH_DLINFO must come first so PPC can do its special alignment of
+	 * AUXV.
+	 * update AT_VECTOR_SIZE_ARCH if the number of NEW_AUX_ENT() in
+	 * ARCH_DLINFO changes
+	 */
+	ARCH_DLINFO;
+#endif
 	NEW_AUX_ENT(AT_HWCAP,	ELF_HWCAP);
 #ifdef ELF_HWCAP2
 	NEW_AUX_ENT(AT_HWCAP2,	ELF_HWCAP2);
@@ -659,17 +640,32 @@ static int create_elf_fdpic_tables(struc
 	NEW_AUX_ENT(AT_EGID,	(elf_addr_t) from_kgid_munged(cred->user_ns, cred->egid));
 	NEW_AUX_ENT(AT_SECURE,	bprm->secureexec);
 	NEW_AUX_ENT(AT_EXECFN,	bprm->exec);
-
-#ifdef ARCH_DLINFO
-	nr = 0;
-	csp -= AT_VECTOR_SIZE_ARCH * 2 * sizeof(unsigned long);
-
-	/* ARCH_DLINFO must come last so platform specific code can enforce
-	 * special alignment requirements on the AUXV if necessary (eg. PPC).
-	 */
-	ARCH_DLINFO;
-#endif
+	if (k_platform) {
+		NEW_AUX_ENT(AT_PLATFORM,
+			    (elf_addr_t)(unsigned long)u_platform);
+	}
+	if (k_base_platform) {
+		NEW_AUX_ENT(AT_BASE_PLATFORM,
+			    (elf_addr_t)(unsigned long)u_base_platform);
+	}
+	if (bprm->have_execfd) {
+		NEW_AUX_ENT(AT_EXECFD, bprm->execfd);
+	}
 #undef NEW_AUX_ENT
+	/* AT_NULL is zero; clear the rest too */
+	memset(elf_info, 0, (char *)mm->saved_auxv +
+	       sizeof(mm->saved_auxv) - (char *)elf_info);
+
+	/* And advance past the AT_NULL entry.  */
+	elf_info += 2;
+
+	ei_index = elf_info - (elf_addr_t *)mm->saved_auxv;
+	csp -= ei_index * sizeof(elf_addr_t);
+
+	/* Put the elf_info on the stack in the right place.  */
+	if (copy_to_user((void __user *)csp, mm->saved_auxv,
+			 ei_index * sizeof(elf_addr_t)))
+		return -EFAULT;
 
 	/* allocate room for argv[] and envv[] */
 	csp -= (bprm->envc + 1) * sizeof(elf_caddr_t);
_

Patches currently in -mm which might be from jcmvbkbc@gmail.com are

binfmt_elf_fdpic-fix-proc-pid-auxv.patch


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