/dev/mem: handle out-of-bounds read/write
authorPetr Tesarik <ptesarik@suse.cz>
Thu, 30 Jan 2014 08:48:02 +0000 (09:48 +0100)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Sat, 15 Feb 2014 19:51:02 +0000 (11:51 -0800)
commit08d2d00b291ed4eb91530050274e67a761c1901d
tree89099e1078b50ff770f06a86106edc72dc52563f
parent1bc9fac3da9aa7569e70e9fda605281ef7e42b9f
/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>
drivers/char/mem.c