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Subject[PATCH] /dev/mem: Fix wrong error on accessing beyond valid memory addresses.
Date
Currently this returns -EFAULT, but it really should be returning 0,
as in - 0 bytes read or written. This is what you would get by
opening a block device, seeking to the end, and trying to read
something. Additionally, make lseek() check the sought-to offset
to pass the valid_phys_addr_range test.

Cc: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Andrei Warkentin <andreiw@vmware.com>
---
drivers/char/mem.c | 9 +++++++--
1 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 8fc04b4..02d0b1a 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -98,7 +98,7 @@ static ssize_t read_mem(struct file *file, char __user *buf,
char *ptr;

if (!valid_phys_addr_range(p, count))
- return -EFAULT;
+ return 0;
read = 0;
#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
/* we don't have page 0 mapped on sparc and m68k.. */
@@ -156,7 +156,7 @@ static ssize_t write_mem(struct file *file, const char __user *buf,
void *ptr;

if (!valid_phys_addr_range(p, count))
- return -EFAULT;
+ return 0;

written = 0;

@@ -710,6 +710,11 @@ static loff_t memory_lseek(struct file *file, loff_t offset, int orig)
case SEEK_CUR:
offset += file->f_pos;
case SEEK_SET:
+ if (!valid_phys_addr_range(offset, 0)) {
+ ret = -EINVAL;
+ break;
+ }
+
/* to avoid userland mistaking f_pos=-9 as -EBADF=-9 */
if ((unsigned long long)offset >= ~0xFFFULL) {
ret = -EOVERFLOW;
--
1.7.4.1


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