linux-hardening - [PATCH][next] powerpc/vas: Fix potential NULL pointer dereference

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Date:   Fri, 15 Oct 2021 00:03:45 -0500
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Nicholas Piggin <npiggin@...il.com>,
        Haren Myneni <haren@...ux.ibm.com>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        linux-hardening@...r.kernel.org
Subject: [PATCH][next] powerpc/vas: Fix potential NULL pointer dereference

(!ptr && !ptr->foo) strikes again. :)

The expression (!ptr && !ptr->foo) is bogus and in case ptr is NULL,
it leads to a NULL pointer dereference: ptr->foo.

Fix this by converting && to ||

This issue was detected with the help of Coccinelle, and audited and
fixed manually.

Fixes: 1a0d0d5ed5e3 ("powerpc/vas: Add platform specific user window operations")
Cc: stable@...r.kernel.org
Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
---
 arch/powerpc/platforms/book3s/vas-api.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/platforms/book3s/vas-api.c b/arch/powerpc/platforms/book3s/vas-api.c
index 30172e52e16b..4d82c92ddd52 100644
--- a/arch/powerpc/platforms/book3s/vas-api.c
+++ b/arch/powerpc/platforms/book3s/vas-api.c
@@ -303,7 +303,7 @@ static int coproc_ioc_tx_win_open(struct file *fp, unsigned long arg)
 		return -EINVAL;
 	}
 
-	if (!cp_inst->coproc->vops && !cp_inst->coproc->vops->open_win) {
+	if (!cp_inst->coproc->vops || !cp_inst->coproc->vops->open_win) {
 		pr_err("VAS API is not registered\n");
 		return -EACCES;
 	}
@@ -373,7 +373,7 @@ static int coproc_mmap(struct file *fp, struct vm_area_struct *vma)
 		return -EINVAL;
 	}
 
-	if (!cp_inst->coproc->vops && !cp_inst->coproc->vops->paste_addr) {
+	if (!cp_inst->coproc->vops || !cp_inst->coproc->vops->paste_addr) {
 		pr_err("%s(): VAS API is not registered\n", __func__);
 		return -EACCES;
 	}
-- 
2.27.0