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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>,
	"Alexander Shishkin" <alexander.shishkin@linux.intel.com>,
	"Jiri Olsa" <jolsa@redhat.com>,
	"Namhyung Kim" <namhyung@kernel.org>,
	"Petr Mladek" <pmladek@suse.com>,
	"Sergey Senozhatsky" <sergey.senozhatsky@gmail.com>,
	"Andy Shevchenko" <andriy.shevchenko@linux.intel.com>,
	"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>,
	"Chinwen Chang" <chinwen.chang@mediatek.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>,
	"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: [PATCH v2 1/7] binfmt: don't use MAP_DENYWRITE when loading shared libraries via uselib()
Date: Mon, 16 Aug 2021 21:48:34 +0200	[thread overview]
Message-ID: <20210816194840.42769-2-david@redhat.com> (raw)
In-Reply-To: <20210816194840.42769-1-david@redhat.com>

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));
 	retval = error;
 	if (error != start_addr)
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 439ed81e755a..6d2c79533631 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1384,7 +1384,7 @@ static int load_elf_library(struct file *file)
 			(eppnt->p_filesz +
 			 ELF_PAGEOFFSET(eppnt->p_vaddr)),
 			PROT_READ | PROT_WRITE | PROT_EXEC,
-			MAP_FIXED_NOREPLACE | MAP_PRIVATE | MAP_DENYWRITE,
+			MAP_FIXED_NOREPLACE | MAP_PRIVATE,
 			(eppnt->p_offset -
 			 ELF_PAGEOFFSET(eppnt->p_vaddr)));
 	if (error != ELF_PAGESTART(eppnt->p_vaddr))
-- 
2.31.1


  reply	other threads:[~2021-08-16 19:49 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 ` David Hildenbrand [this message]
2021-09-05 15:32   ` [PATCH v2 1/7] binfmt: don't use MAP_DENYWRITE when loading shared libraries via uselib() Guenter Roeck
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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