ipr: Fix out-of-bounds null overwrite

commit d63c7dd5bcb9441af0526d370c43a65ca2c980d9 upstream.

Return value of snprintf is not bound by size value, 2nd argument.
(https://www.kernel.org/doc/htmldocs/kernel-api/API-snprintf.html).
Return value is number of printed chars, can be larger than 2nd
argument.  Therefore, it can write null byte out of bounds ofbuffer.
Since snprintf puts null, it does not need to put additional null byte.

Signed-off-by: Insu Yun <wuninsu@gmail.com>
Reviewed-by: Shane Seymour <shane.seymour@hpe.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

diff --git a/drivers/scsi/ipr.c b/drivers/scsi/ipr.c
index d2c3fdcf90ba334688cb206251354cc8265c5b30..824e66d7bf93e583f67c80eda9b6afd9ad2c2076 100644 (file)
--- a/drivers/scsi/ipr.c
+++ b/drivers/scsi/ipr.c
@@ -3984,13 +3984,12 @@ static ssize_t ipr_store_update_fw(struct device *dev,
        struct ipr_sglist *sglist;
        char fname[100];
        char *src;
-       int len, result, dnld_size;
+       int result, dnld_size;
 
        if (!capable(CAP_SYS_ADMIN))
                return -EACCES;
 
-       len = snprintf(fname, 99, "%s", buf);
-       fname[len-1] = '\0';
+       snprintf(fname, sizeof(fname), "%s", buf);
 
        if (request_firmware(&fw_entry, fname, &ioa_cfg->pdev->dev)) {
                dev_err(&ioa_cfg->pdev->dev, "Firmware file %s not found\n", fname);