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    Subject[PATCH 5.4 158/475] udmabuf: validate ubuf->pagecount
    Date
    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 9635897458a0..e553c6a937f6 100644
    --- a/drivers/dma-buf/udmabuf.c
    +++ b/drivers/dma-buf/udmabuf.c
    @@ -145,6 +145,10 @@ static long udmabuf_create(const struct udmabuf_create_list *head,
    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


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