From: Petr Tesarik <ptesarik@xxxxxxx> 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 <ptesarik@xxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Jiri Slaby <jslaby@xxxxxxx> --- 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 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html