From: Petr Tesarik <ptesa...@suse.cz>
3.12-stable review patch. If anyone has any objections, please let me know.
===============
commit 08d2d00b291ed4eb91530050274e67a761c1901d upstream.
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 <ptesa...@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
Signed-off-by: Jiri Slaby <jsl...@suse.cz>
---
drivers/char/mem.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index f895a8c8a244..d1f4675809f8 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -100,6 +100,9 @@ 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;
@@ -158,6 +161,9 @@ 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;
--
1.9.2
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