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char: ppdev: Fix a possible null-pointer dereference in pp_release()

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In pp_release(), there is an if statement on line 730 to check whether
pp->pdev is NULL:
    else if ((pp->flags & PP_CLAIMED) && pp->pdev && ...)

When pp->pdev is NULL, it is used on line 743:
    info = &pp->pdev->port->ieee1284;
and on line 748:
    parport_release(pp->pdev);

Thus, a possible null-pointer dereference may occur.

To fix this bug, pp->pdev is checked on line 740.

This bug is found by a static analysis tool STCheck written by us.

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Link: https://lore.kernel.org/r/20190724090426.1401-1-baijiaju1990@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jia-Ju Bai 2019-07-24 17:04:26 +08:00 committed by Greg Kroah-Hartman
parent 092f47c383
commit 7bdd969597
1 changed files with 1 additions and 1 deletions
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2
drivers/char/ppdev.c
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@ -737,7 +737,7 @@ static int pp_release(struct inode *inode, struct file *file)
"negotiated back to compatibility mode because user-space forgot\n");
}
if (pp->flags & PP_CLAIMED) {
if ((pp->flags & PP_CLAIMED) && pp->pdev) {
struct ieee1284_info *info;
info = &pp->pdev->port->ieee1284;