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/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>
This commit is contained in:
Petr Tesarik 2014-01-30 09:48:02 +01:00 committed by Greg Kroah-Hartman
parent 1bc9fac3da
commit 08d2d00b29
1 changed files with 6 additions and 0 deletions
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6
drivers/char/mem.c
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@ -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;