4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> commit fc14eebfc20854a38fd9f1d93a42b1783dad4d17 upstream. syzbot is reporting NULL pointer dereference at snapshot_write() [1]. This is because data->handle is zero-cleared by ioctl(SNAPSHOT_FREE). Fix this by checking data_of(data->handle) != NULL before using it. [1] https://syzkaller.appspot.com/bug?id=828a3c71bd344a6de8b6a31233d51a72099f27fd Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> Reported-by: syzbot <syzbot+ae590932da6e45d6564d@xxxxxxxxxxxxxxxxxxxxxxxxx> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- kernel/power/user.c | 5 +++++ 1 file changed, 5 insertions(+) --- a/kernel/power/user.c +++ b/kernel/power/user.c @@ -184,6 +184,11 @@ static ssize_t snapshot_write(struct fil res = PAGE_SIZE - pg_offp; } + if (!data_of(data->handle)) { + res = -EINVAL; + goto unlock; + } + res = simple_write_to_buffer(data_of(data->handle), res, &pg_offp, buf, count); if (res > 0)
