From: Omar Sandoval <osandov@osandov.com>
To: linux-fsdevel@vger.kernel.org, linux-btrfs@vger.kernel.org
Cc: Dave Chinner <david@fromorbit.com>, Jann Horn <jannh@google.com>,
linux-api@vger.kernel.org, kernel-team@fb.com
Subject: [RFC PATCH v2 1/5] fs: add O_ENCODED open flag
Date: Tue, 15 Oct 2019 11:42:39 -0700 [thread overview]
Message-ID: <c4d2e911b7b04df9aa8418c8b11bc4c194e3808c.1571164762.git.osandov@fb.com> (raw)
In-Reply-To: <cover.1571164762.git.osandov@fb.com>
From: Omar Sandoval <osandov@fb.com>
The upcoming RWF_ENCODED operation introduces some security concerns:
1. Compressed writes will pass arbitrary data to decompression
algorithms in the kernel.
2. Compressed reads can leak truncated/hole punched data.
Therefore, we need to require privilege for RWF_ENCODED. It's not
possible to do the permissions checks at the time of the read or write
because, e.g., io_uring submits IO from a worker thread. So, add an open
flag which requires CAP_SYS_ADMIN. It can also be set and cleared with
fcntl(). The flag is not cleared in any way on fork or exec; it should
probably be used with O_CLOEXEC in most cases.
Note that the usual issue that unknown open flags are ignored doesn't
really matter for O_ENCODED; if the kernel doesn't support O_ENCODED,
then it doesn't support RWF_ENCODED, either.
Signed-off-by: Omar Sandoval <osandov@fb.com>
---
fs/fcntl.c | 10 ++++++++--
fs/namei.c | 4 ++++
include/linux/fcntl.h | 2 +-
include/uapi/asm-generic/fcntl.h | 4 ++++
4 files changed, 17 insertions(+), 3 deletions(-)
diff --git a/fs/fcntl.c b/fs/fcntl.c
index 3d40771e8e7c..45ebc6df078e 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -30,7 +30,8 @@
#include <asm/siginfo.h>
#include <linux/uaccess.h>
-#define SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | O_DIRECT | O_NOATIME)
+#define SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | O_DIRECT | O_NOATIME | \
+ O_ENCODED)
static int setfl(int fd, struct file * filp, unsigned long arg)
{
@@ -49,6 +50,11 @@ static int setfl(int fd, struct file * filp, unsigned long arg)
if (!inode_owner_or_capable(inode))
return -EPERM;
+ /* O_ENCODED can only be set by superuser */
+ if ((arg & O_ENCODED) && !(filp->f_flags & O_ENCODED) &&
+ !capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
/* required for strict SunOS emulation */
if (O_NONBLOCK != O_NDELAY)
if (arg & O_NDELAY)
@@ -1031,7 +1037,7 @@ static int __init fcntl_init(void)
* Exceptions: O_NONBLOCK is a two bit define on parisc; O_NDELAY
* is defined as O_NONBLOCK on some platforms and not on others.
*/
- BUILD_BUG_ON(21 - 1 /* for O_RDONLY being 0 */ !=
+ BUILD_BUG_ON(22 - 1 /* for O_RDONLY being 0 */ !=
HWEIGHT32(
(VALID_OPEN_FLAGS & ~(O_NONBLOCK | O_NDELAY)) |
__FMODE_EXEC | __FMODE_NONOTIFY));
diff --git a/fs/namei.c b/fs/namei.c
index 671c3c1a3425..ae86b125888a 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2978,6 +2978,10 @@ static int may_open(const struct path *path, int acc_mode, int flag)
if (flag & O_NOATIME && !inode_owner_or_capable(inode))
return -EPERM;
+ /* O_ENCODED can only be set by superuser */
+ if ((flag & O_ENCODED) && !capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
return 0;
}
diff --git a/include/linux/fcntl.h b/include/linux/fcntl.h
index d019df946cb2..5fac02479639 100644
--- a/include/linux/fcntl.h
+++ b/include/linux/fcntl.h
@@ -9,7 +9,7 @@
(O_RDONLY | O_WRONLY | O_RDWR | O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC | \
O_APPEND | O_NDELAY | O_NONBLOCK | O_NDELAY | __O_SYNC | O_DSYNC | \
FASYNC | O_DIRECT | O_LARGEFILE | O_DIRECTORY | O_NOFOLLOW | \
- O_NOATIME | O_CLOEXEC | O_PATH | __O_TMPFILE)
+ O_NOATIME | O_CLOEXEC | O_PATH | __O_TMPFILE | O_ENCODED)
#ifndef force_o_largefile
#define force_o_largefile() (!IS_ENABLED(CONFIG_ARCH_32BIT_OFF_T))
diff --git a/include/uapi/asm-generic/fcntl.h b/include/uapi/asm-generic/fcntl.h
index 9dc0bf0c5a6e..8c5cbd5942e3 100644
--- a/include/uapi/asm-generic/fcntl.h
+++ b/include/uapi/asm-generic/fcntl.h
@@ -97,6 +97,10 @@
#define O_NDELAY O_NONBLOCK
#endif
+#ifndef O_ENCODED
+#define O_ENCODED 040000000
+#endif
+
#define F_DUPFD 0 /* dup */
#define F_GETFD 1 /* get close_on_exec */
#define F_SETFD 2 /* set/clear close_on_exec */
--
2.23.0
next prev parent reply other threads:[~2019-10-15 18:43 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-15 18:42 [RFC PATCH v2 0/5] fs: interface for directly reading/writing compressed data Omar Sandoval
2019-10-15 18:42 ` [PATCH man-pages] Document encoded I/O Omar Sandoval
2019-10-20 23:05 ` [RFC PATCH v2 0/5] fs: interface for directly reading/writing compressed data Dave Chinner
2019-10-21 19:04 ` Omar Sandoval
2019-10-21 6:18 ` [PATCH man-pages] Document encoded I/O Amir Goldstein
2019-10-21 18:53 ` Omar Sandoval
2019-10-22 6:40 ` Amir Goldstein
2019-10-23 4:44 ` Aleksa Sarai
2019-10-23 6:06 ` Amir Goldstein
2019-10-23 12:12 ` Aleksa Sarai
2019-10-30 22:46 ` Omar Sandoval
2019-10-30 22:57 ` Omar Sandoval
2019-10-15 18:42 ` Omar Sandoval [this message]
2019-10-19 4:50 ` [RFC PATCH v2 1/5] fs: add O_ENCODED open flag Aleksa Sarai
2019-10-23 4:46 ` Aleksa Sarai
2019-10-30 22:55 ` Omar Sandoval
2019-10-30 23:17 ` Aleksa Sarai
2019-10-15 18:42 ` [RFC PATCH v2 2/5] fs: add RWF_ENCODED for reading/writing compressed data Omar Sandoval
2019-10-16 9:50 ` Nikolay Borisov
2019-10-18 22:19 ` Omar Sandoval
2019-10-19 5:01 ` Aleksa Sarai
2019-10-21 18:28 ` Darrick J. Wong
2019-10-21 18:38 ` Aleksa Sarai
2019-10-21 19:00 ` Darrick J. Wong
2019-10-22 1:37 ` Aleksa Sarai
2019-10-30 22:21 ` Omar Sandoval
2019-10-22 2:02 ` Aleksa Sarai
2019-10-30 22:26 ` Omar Sandoval
2019-10-30 23:11 ` Aleksa Sarai
2019-10-21 19:07 ` Omar Sandoval
2019-10-15 18:42 ` [RFC PATCH v2 3/5] btrfs: generalize btrfs_lookup_bio_sums_dio() Omar Sandoval
2019-10-16 9:22 ` Nikolay Borisov
2019-10-18 22:19 ` Omar Sandoval
2019-10-15 18:42 ` [RFC PATCH v2 4/5] btrfs: implement RWF_ENCODED reads Omar Sandoval
2019-10-16 11:10 ` Nikolay Borisov
2019-10-18 22:23 ` Omar Sandoval
2019-10-15 18:42 ` [RFC PATCH v2 5/5] btrfs: implement RWF_ENCODED writes Omar Sandoval
2019-10-16 10:44 ` Nikolay Borisov
2019-10-18 22:55 ` Omar Sandoval
2019-10-18 23:33 ` Omar Sandoval
2019-10-21 13:14 ` David Sterba
2019-10-21 18:05 ` Omar Sandoval
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