From: David Hildenbrand <david@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: "David Hildenbrand" <david@redhat.com>,
"Linus Torvalds" <torvalds@linux-foundation.org>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Ingo Molnar" <mingo@redhat.com>,
"Borislav Petkov" <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>,
"Alexander Viro" <viro@zeniv.linux.org.uk>,
"Alexey Dobriyan" <adobriyan@gmail.com>,
"Steven Rostedt" <rostedt@goodmis.org>,
"Peter Zijlstra" <peterz@infradead.org>,
"Arnaldo Carvalho de Melo" <acme@kernel.org>,
"Mark Rutland" <mark.rutland@arm.com>,
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"Rasmus Villemoes" <linux@rasmusvillemoes.dk>,
"Kees Cook" <keescook@chromium.org>,
"Eric W. Biederman" <ebiederm@xmission.com>,
"Greg Ungerer" <gerg@linux-m68k.org>,
"Geert Uytterhoeven" <geert@linux-m68k.org>,
"Mike Rapoport" <rppt@kernel.org>,
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"Chinwen Chang" <chinwen.chang@mediatek.com>,
"Michel Lespinasse" <walken@google.com>,
"Catalin Marinas" <catalin.marinas@arm.com>,
"Matthew Wilcox (Oracle)" <willy@infradead.org>,
"Huang Ying" <ying.huang@intel.com>,
"Jann Horn" <jannh@google.com>, "Feng Tang" <feng.tang@intel.com>,
"Kevin Brodsky" <Kevin.Brodsky@arm.com>,
"Michael Ellerman" <mpe@ellerman.id.au>,
"Shawn Anastasio" <shawn@anastas.io>,
"Steven Price" <steven.price@arm.com>,
"Nicholas Piggin" <npiggin@gmail.com>,
"Christian Brauner" <christian.brauner@ubuntu.com>,
"Jens Axboe" <axboe@kernel.dk>,
"Gabriel Krisman Bertazi" <krisman@collabora.com>,
"Peter Xu" <peterx@redhat.com>,
"Suren Baghdasaryan" <surenb@google.com>,
"Shakeel Butt" <shakeelb@google.com>,
"Marco Elver" <elver@google.com>,
"Daniel Jordan" <daniel.m.jordan@oracle.com>,
"Nicolas Viennot" <Nicolas.Viennot@twosigma.com>,
"Thomas Cedeno" <thomascedeno@google.com>,
"Collin Fijalkovich" <cfijalkovich@google.com>,
"Michal Hocko" <mhocko@suse.com>,
"Miklos Szeredi" <miklos@szeredi.hu>,
"Chengguang Xu" <cgxu519@mykernel.net>,
"Christian König" <ckoenig.leichtzumerken@gmail.com>,
linux-unionfs@vger.kernel.org, linux-api@vger.kernel.org,
x86@kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org
Subject: [PATCH v1 4/7] binfmt: remove in-tree usage of MAP_DENYWRITE
Date: Thu, 12 Aug 2021 10:43:45 +0200 [thread overview]
Message-ID: <20210812084348.6521-5-david@redhat.com> (raw)
In-Reply-To: <20210812084348.6521-1-david@redhat.com>
At exec time when we mmap the new executable via MAP_DENYWRITE we have it
opened via do_open_execat() and already deny_write_access()'ed the file
successfully. Once exec completes, we allow_write_acces(); however,
we set mm->exe_file in begin_new_exec() via set_mm_exe_file() and
also deny_write_access() as long as mm->exe_file remains set. We'll
effectively deny write access to our executable via mm->exe_file
until mm->exe_file is changed -- when the process is removed, on new
exec, or via sys_prctl(PR_SET_MM_EXE_FILE).
Let's remove all usage of MAP_DENYWRITE, it's no longer necessary for
mm->exe_file.
In case of an elf interpreter, we'll now only deny write access to the file
during exec. This is somewhat okay, because the interpreter behaves
(and sometime is) a shared library; all shared libraries, especially the
ones loaded directly in user space like via dlopen() won't ever be mapped
via MAP_DENYWRITE, because we ignore that from user space completely;
these shared libraries can always be modified while mapped and executed.
Let's only special-case the main executable, denying write access while
being executed by a process. This can be considered a minor user space
visible change.
While this is a cleanup, it also fixes part of a problem reported with
VM_DENYWRITE on overlayfs, as VM_DENYWRITE is effectively unused with
this patch and will be removed next:
"Overlayfs did not honor positive i_writecount on realfile for
VM_DENYWRITE mappings." [1]
[1] https://lore.kernel.org/r/YNHXzBgzRrZu1MrD@miu.piliscsaba.redhat.com/
Reported-by: Chengguang Xu <cgxu519@mykernel.net>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
arch/x86/ia32/ia32_aout.c | 6 ++----
fs/binfmt_aout.c | 5 ++---
fs/binfmt_elf.c | 4 ++--
fs/binfmt_elf_fdpic.c | 2 +-
4 files changed, 7 insertions(+), 10 deletions(-)
diff --git a/arch/x86/ia32/ia32_aout.c b/arch/x86/ia32/ia32_aout.c
index 321d7b22ad2d..9bd15241fadb 100644
--- a/arch/x86/ia32/ia32_aout.c
+++ b/arch/x86/ia32/ia32_aout.c
@@ -202,8 +202,7 @@ static int load_aout_binary(struct linux_binprm *bprm)
error = vm_mmap(bprm->file, N_TXTADDR(ex), ex.a_text,
PROT_READ | PROT_EXEC,
- MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE |
- MAP_32BIT,
+ MAP_FIXED | MAP_PRIVATE | MAP_32BIT,
fd_offset);
if (error != N_TXTADDR(ex))
@@ -211,8 +210,7 @@ static int load_aout_binary(struct linux_binprm *bprm)
error = vm_mmap(bprm->file, N_DATADDR(ex), ex.a_data,
PROT_READ | PROT_WRITE | PROT_EXEC,
- MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE |
- MAP_32BIT,
+ MAP_FIXED | MAP_PRIVATE | MAP_32BIT,
fd_offset + ex.a_text);
if (error != N_DATADDR(ex))
return error;
diff --git a/fs/binfmt_aout.c b/fs/binfmt_aout.c
index d29de971d3f3..a47496d0f123 100644
--- a/fs/binfmt_aout.c
+++ b/fs/binfmt_aout.c
@@ -221,8 +221,7 @@ static int load_aout_binary(struct linux_binprm * bprm)
}
error = vm_mmap(bprm->file, N_TXTADDR(ex), ex.a_text,
- PROT_READ | PROT_EXEC,
- MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE,
+ PROT_READ | PROT_EXEC, MAP_FIXED | MAP_PRIVATE,
fd_offset);
if (error != N_TXTADDR(ex))
@@ -230,7 +229,7 @@ static int load_aout_binary(struct linux_binprm * bprm)
error = vm_mmap(bprm->file, N_DATADDR(ex), ex.a_data,
PROT_READ | PROT_WRITE | PROT_EXEC,
- MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE,
+ MAP_FIXED | MAP_PRIVATE,
fd_offset + ex.a_text);
if (error != N_DATADDR(ex))
return error;
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 6d2c79533631..69d900a8473d 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -622,7 +622,7 @@ static unsigned long load_elf_interp(struct elfhdr *interp_elf_ex,
eppnt = interp_elf_phdata;
for (i = 0; i < interp_elf_ex->e_phnum; i++, eppnt++) {
if (eppnt->p_type == PT_LOAD) {
- int elf_type = MAP_PRIVATE | MAP_DENYWRITE;
+ int elf_type = MAP_PRIVATE;
int elf_prot = make_prot(eppnt->p_flags, arch_state,
true, true);
unsigned long vaddr = 0;
@@ -1070,7 +1070,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
elf_prot = make_prot(elf_ppnt->p_flags, &arch_state,
!!interpreter, false);
- elf_flags = MAP_PRIVATE | MAP_DENYWRITE;
+ elf_flags = MAP_PRIVATE;
vaddr = elf_ppnt->p_vaddr;
/*
diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
index cf4028487dcc..6d8fd6030cbb 100644
--- a/fs/binfmt_elf_fdpic.c
+++ b/fs/binfmt_elf_fdpic.c
@@ -1041,7 +1041,7 @@ static int elf_fdpic_map_file_by_direct_mmap(struct elf_fdpic_params *params,
if (phdr->p_flags & PF_W) prot |= PROT_WRITE;
if (phdr->p_flags & PF_X) prot |= PROT_EXEC;
- flags = MAP_PRIVATE | MAP_DENYWRITE;
+ flags = MAP_PRIVATE;
maddr = 0;
switch (params->flags & ELF_FDPIC_FLAG_ARRANGEMENT) {
--
2.31.1
next prev parent reply other threads:[~2021-08-12 8:45 UTC|newest]
Thread overview: 82+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-12 8:43 [PATCH v1 0/7] Remove in-tree usage of MAP_DENYWRITE David Hildenbrand
2021-08-12 8:43 ` [PATCH v1 1/7] binfmt: don't use MAP_DENYWRITE when loading shared libraries via uselib() David Hildenbrand
2021-08-12 8:43 ` [PATCH v1 2/7] kernel/fork: factor out atomcially replacing the current MM exe_file David Hildenbrand
2021-08-12 9:17 ` Christian Brauner
2021-08-12 8:43 ` [PATCH v1 3/7] kernel/fork: always deny write access to " David Hildenbrand
2021-08-12 10:05 ` Christian Brauner
2021-08-12 10:13 ` David Hildenbrand
2021-08-12 12:32 ` Christian Brauner
2021-08-12 12:38 ` David Hildenbrand
2021-08-12 16:51 ` Linus Torvalds
2021-08-12 19:38 ` David Hildenbrand
2021-08-12 8:43 ` David Hildenbrand [this message]
2021-08-12 8:43 ` [PATCH v1 5/7] mm: remove VM_DENYWRITE David Hildenbrand
2021-08-12 8:43 ` [PATCH v1 6/7] mm: ignore MAP_DENYWRITE in ksys_mmap_pgoff() David Hildenbrand
2021-08-12 8:43 ` [PATCH v1 7/7] fs: update documentation of get_write_access() and friends David Hildenbrand
2021-08-12 12:20 ` [PATCH v1 0/7] Remove in-tree usage of MAP_DENYWRITE Florian Weimer
2021-08-12 12:47 ` David Hildenbrand
2021-08-12 16:17 ` Eric W. Biederman
2021-08-12 17:32 ` Eric W. Biederman
2021-08-12 17:35 ` Andy Lutomirski
2021-08-12 17:48 ` Eric W. Biederman
2021-08-12 18:01 ` Andy Lutomirski
2021-08-12 18:10 ` Linus Torvalds
2021-08-12 18:47 ` Eric W. Biederman
2021-08-13 9:05 ` David Laight
[not found] ` <87h7ft2j68.fsf@disp2133>
2021-08-13 20:51 ` Florian Weimer
2021-08-14 0:31 ` Linus Torvalds
2021-08-14 0:49 ` Andy Lutomirski
2021-08-14 0:54 ` Linus Torvalds
2021-08-14 0:58 ` Linus Torvalds
2021-08-14 1:57 ` Al Viro
2021-08-14 2:02 ` Al Viro
2021-08-14 9:06 ` David Hildenbrand
2021-08-14 7:53 ` Christian Brauner
2021-08-14 19:52 ` David Laight
2021-08-26 17:48 ` Andy Lutomirski
2021-08-26 21:47 ` David Hildenbrand
2021-08-26 22:13 ` Eric W. Biederman
2021-08-27 8:22 ` David Laight
2021-08-27 15:58 ` Eric W. Biederman
2021-09-01 8:28 ` David Hildenbrand
2021-08-27 10:18 ` Christian Brauner
2021-08-14 3:04 ` Matthew Wilcox
2021-08-17 16:48 ` Removing Mandatory Locks Eric W. Biederman
2021-08-17 16:50 ` David Hildenbrand
2021-08-18 9:34 ` Rodrigo Campos
2021-08-19 19:18 ` Jeff Layton
2021-08-19 20:03 ` Willy Tarreau
2021-08-19 18:39 ` Jeff Layton
2021-08-19 19:15 ` Linus Torvalds
2021-08-19 19:55 ` Eric Biggers
2021-08-19 20:18 ` Jeff Layton
2021-08-19 20:31 ` Linus Torvalds
2021-08-19 21:43 ` Jeff Layton
2021-08-19 22:32 ` Linus Torvalds
2021-08-20 8:30 ` David Laight
2021-08-23 7:55 ` Geert Uytterhoeven
2021-08-23 8:14 ` David Laight
2021-08-20 13:43 ` Steven Rostedt
2021-08-20 16:06 ` Linus Torvalds
2021-08-20 2:10 ` Matthew Wilcox
2021-08-20 6:36 ` Amir Goldstein
2021-08-20 7:14 ` Amir Goldstein
2021-08-20 12:27 ` Jeff Layton
2021-08-20 12:38 ` Willy Tarreau
2021-08-20 13:03 ` Jeff Layton
2021-08-20 13:11 ` Willy Tarreau
2021-08-20 16:30 ` Kees Cook
2021-08-20 19:17 ` H. Peter Anvin
2021-08-20 21:29 ` Jeff Layton
2021-08-21 12:45 ` Jeff Layton
2021-08-23 22:15 ` J. Bruce Fields
2021-08-20 22:31 ` Matthew Wilcox
2021-08-18 7:51 ` [PATCH v1 0/7] Remove in-tree usage of MAP_DENYWRITE Christian Brauner
2021-08-18 15:42 ` J. Bruce Fields
2021-08-19 13:56 ` Eric W. Biederman
2021-08-19 14:33 ` J. Bruce Fields
2021-08-20 12:54 ` Jeff Layton
[not found] ` <162943109106.9892.7426782042253067338@noble.neil.brown.name>
2021-08-20 8:25 ` David Laight
2021-08-12 19:24 ` David Hildenbrand
2021-08-12 18:15 ` Florian Weimer
2021-08-12 18:21 ` Linus Torvalds
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