From: Guenter Roeck <linux@roeck-us.net>
To: David Hildenbrand <david@redhat.com>
Cc: linux-kernel@vger.kernel.org,
"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>,
"Alexander Shishkin" <alexander.shishkin@linux.intel.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>,
"Vlastimil Babka" <vbabka@suse.cz>,
"Vincenzo Frascino" <vincenzo.frascino@arm.com>,
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"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>,
"Michal Hocko" <mhocko@suse.com>,
"Miklos Szeredi" <miklos@szeredi.hu>,
"Chengguang Xu" <cgxu519@mykernel.net>,
"Christian König" <ckoenig.leichtzumerken@gmail.com>,
"Florian Weimer" <fweimer@redhat.com>,
"David Laight" <David.Laight@ACULAB.COM>,
linux-unionfs@vger.kernel.org, linux-api@vger.kernel.org,
x86@kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org
Subject: Re: [PATCH v2 1/7] binfmt: don't use MAP_DENYWRITE when loading shared libraries via uselib()
Date: Sun, 5 Sep 2021 08:32:29 -0700 [thread overview]
Message-ID: <20210905153229.GA3019909@roeck-us.net> (raw)
In-Reply-To: <20210816194840.42769-2-david@redhat.com>
On Mon, Aug 16, 2021 at 09:48:34PM +0200, David Hildenbrand wrote:
> uselib() is the legacy systemcall for loading shared libraries.
> Nowadays, applications use dlopen() to load shared libraries, completely
> implemented in user space via mmap().
>
> For example, glibc uses MAP_COPY to mmap shared libraries. While this
> maps to MAP_PRIVATE | MAP_DENYWRITE on Linux, Linux ignores any
> MAP_DENYWRITE specification from user space in mmap.
>
> With this change, all remaining in-tree users of MAP_DENYWRITE use it
> to map an executable. We will be able to open shared libraries loaded
> via uselib() writable, just as we already can via dlopen() from user
> space.
>
> This is one step into the direction of removing MAP_DENYWRITE from the
> kernel. This can be considered a minor user space visible change.
>
> Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
> arch/x86/ia32/ia32_aout.c | 2 +-
> fs/binfmt_aout.c | 2 +-
> fs/binfmt_elf.c | 2 +-
> 3 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/ia32/ia32_aout.c b/arch/x86/ia32/ia32_aout.c
> index 5e5b9fc2747f..321d7b22ad2d 100644
> --- a/arch/x86/ia32/ia32_aout.c
> +++ b/arch/x86/ia32/ia32_aout.c
> @@ -293,7 +293,7 @@ static int load_aout_library(struct file *file)
> /* Now use mmap to map the library into memory. */
> error = vm_mmap(file, start_addr, ex.a_text + ex.a_data,
> PROT_READ | PROT_WRITE | PROT_EXEC,
> - MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE | MAP_32BIT,
> + MAP_FIXED | MAP_PRIVATE | MAP_32BIT,
> N_TXTOFF(ex));
> retval = error;
> if (error != start_addr)
> diff --git a/fs/binfmt_aout.c b/fs/binfmt_aout.c
> index 145917f734fe..d29de971d3f3 100644
> --- a/fs/binfmt_aout.c
> +++ b/fs/binfmt_aout.c
> @@ -309,7 +309,7 @@ static int load_aout_library(struct file *file)
> /* Now use mmap to map the library into memory. */
> error = vm_mmap(file, start_addr, ex.a_text + ex.a_data,
> PROT_READ | PROT_WRITE | PROT_EXEC,
> - MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE,
> + MAP_FIXED | MAP_PRIVATE;
> N_TXTOFF(ex));
Guess someone didn't care compile testing their code. This is now in
mainline.
Guenter
next prev parent reply other threads:[~2021-09-05 15:32 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-16 19:48 [PATCH v2 0/7] Remove in-tree usage of MAP_DENYWRITE David Hildenbrand
2021-08-16 19:48 ` [PATCH v2 1/7] binfmt: don't use MAP_DENYWRITE when loading shared libraries via uselib() David Hildenbrand
2021-09-05 15:32 ` Guenter Roeck [this message]
2021-09-05 17:17 ` Linus Torvalds
2021-09-05 19:07 ` David Hildenbrand
2021-08-16 19:48 ` [PATCH v2 2/7] kernel/fork: factor out replacing the current MM exe_file David Hildenbrand
2021-08-19 20:51 ` Linus Torvalds
2021-08-20 8:46 ` David Hildenbrand
2021-08-20 14:36 ` Eric W. Biederman
2021-08-22 17:58 ` Linus Torvalds
2021-08-16 19:48 ` [PATCH v2 3/7] kernel/fork: always deny write access to " David Hildenbrand
2021-08-16 19:48 ` [PATCH v2 4/7] binfmt: remove in-tree usage of MAP_DENYWRITE David Hildenbrand
2021-08-16 19:48 ` [PATCH v2 5/7] mm: remove VM_DENYWRITE David Hildenbrand
2021-08-16 19:48 ` [PATCH v2 6/7] mm: ignore MAP_DENYWRITE in ksys_mmap_pgoff() David Hildenbrand
2021-08-16 19:48 ` [PATCH v2 7/7] fs: update documentation of get_write_access() and friends David Hildenbrand
2021-08-17 11:01 ` [PATCH v2 0/7] Remove in-tree usage of MAP_DENYWRITE Christian König
2021-09-03 9:45 ` David Hildenbrand
2021-09-03 16:26 ` Linus Torvalds
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