parisc: isa-eeprom - Fix loff_t usage

loff_t is a signed type. If userspace passes a negative ppos, the "count"
range check is weakened. "count"s bigger than HPEE_MAX_LENGTH will pass the check.
Also, if ppos is negative, the readb(eisa_eeprom_addr + *ppos) will poke in random
memory.

Signed-off-by: Michael Buesch <mb@bu3sch.de>
Cc: stable@kernel.org
Signed-off-by: Helge Deller <deller@gmx.de>

1 files changed, 1 insertions, 1 deletions

diff --git a/drivers/parisc/eisa_eeprom.c b/drivers/parisc/eisa_eeprom.c
index 685d94e69d4..8c0b26e9b98 100644
--- a/drivers/parisc/eisa_eeprom.c
+++ b/drivers/parisc/eisa_eeprom.c
@@ -55,7 +55,7 @@ static ssize_t eisa_eeprom_read(struct file * file,
         ssize_t ret;
         int i;
         
-        if (*ppos >= HPEE_MAX_LENGTH)
+        if (*ppos < 0 || *ppos >= HPEE_MAX_LENGTH)
                 return 0;
         
         count = *ppos + count < HPEE_MAX_LENGTH ? count : HPEE_MAX_LENGTH - *ppos;