[PATCH 5.17 0439/1126] udmabuf: validate ubuf->pagecount

Greg Kroah-Hartman
2022-04-05T08:02:29Z

From: Pavel Skripkin <paskripkin@gmail.com>

[ Upstream commit 2b6dd600dd72573c23ea180b5b0b2f1813405882 ]

Syzbot has reported GPF in sg_alloc_append_table_from_pages(). The
problem was in ubuf->pages == ZERO_PTR.

ubuf->pagecount is calculated from arguments passed from user-space. If
user creates udmabuf with list.size == 0 then ubuf->pagecount will be
also equal to zero; it causes kmalloc_array() to return ZERO_PTR.

Fix it by validating ubuf->pagecount before passing it to
kmalloc_array().

Fixes: fbb0de795078 ("Add udmabuf misc device")
Reported-and-tested-by: syzbot+2c56b725ec547fa9cb29@syzkaller.appspotmail.com
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20211230142649.23022-1-paskripkin@gmail.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/dma-buf/udmabuf.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
index c57a609db75b..e7330684d3b8 100644
--- a/drivers/dma-buf/udmabuf.c
+++ b/drivers/dma-buf/udmabuf.c
@@ -190,6 +190,10 @@ static long udmabuf_create(struct miscdevice *device,
if (ubuf->pagecount > pglimit)
goto err;
}
+
+ if (!ubuf->pagecount)
+ goto err;
+
ubuf->pages = kmalloc_array(ubuf->pagecount, sizeof(*ubuf->pages),
GFP_KERNEL);
if (!ubuf->pages) {
--
2.34.1