linux-kernel - [PATCH] /dev/mem: handle out-of-bounds read/write

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20140130094802.4ee29435@hananiah.suse.cz>
Date:	Thu, 30 Jan 2014 09:48:02 +0100
From:	Petr Tesarik <ptesarik@...e.cz>
To:	Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] /dev/mem: handle out-of-bounds read/write

The loff_t type may be wider than phys_addr_t (e.g. on 32-bit systems).
Consequently, the file offset may be truncated in the assignment.
Currently, /dev/mem wraps around, which may cause applications to read
or write incorrect regions of memory by accident.

Let's follow POSIX file semantics here and return 0 when reading from
and -EFBIG when writing to an offset that cannot be represented by a
phys_addr_t.

Note that the conditional is optimized out by the compiler if loff_t
has the same size as phys_addr_t.

Signed-off-by: Petr Tesarik <ptesarik@...e.cz>
---
 drivers/char/mem.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 92c5937..917403f 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -99,6 +99,9 @@ static ssize_t read_mem(struct file *file, char
__user *buf, ssize_t read, sz;
 	char *ptr;
 
+	if (p != *ppos)
+		return 0;
+
 	if (!valid_phys_addr_range(p, count))
 		return -EFAULT;
 	read = 0;
@@ -157,6 +160,9 @@ static ssize_t write_mem(struct file *file, const
char __user *buf, unsigned long copied;
 	void *ptr;
 
+	if (p != *ppos)
+		return -EFBIG;
+
 	if (!valid_phys_addr_range(p, count))
 		return -EFAULT;
 
-- 
1.8.4.5
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/