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authorPetr Tesarik <ptesarik@suse.cz>2014-01-30 12:48:02 +0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-02-15 23:51:02 +0400
commit08d2d00b291ed4eb91530050274e67a761c1901d (patch)
tree89099e1078b50ff770f06a86106edc72dc52563f
parent1bc9fac3da9aa7569e70e9fda605281ef7e42b9f (diff)
downloadlinux-08d2d00b291ed4eb91530050274e67a761c1901d.tar.xz
/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@suse.cz> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/char/mem.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 92c5937f80c3..917403fe10da 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;