This is another instance of incorrect use of list iterator and checking it for NULL.

The list iterator value 'map' will *always* be set and non-NULL by list_for_each_entry(), so it is incorrect to assume that the iterator value will be NULL if the list is empty (in this case, the check 'if (!map) {' will always be false and never exit as expected).

To fix the bug, use a new variable 'iter' as the list iterator, while use the original variable 'map' as a dedicated pointer to point to the found element.

Without this patch, Kernel crashes with below trace:

Unable to handle kernel access to user memory outside uaccess routines at virtual address 0000ffff7fb03750 ... Call trace: fastrpc_map_create+0x70/0x290 [fastrpc] fastrpc_req_mem_map+0xf0/0x2dc [fastrpc] fastrpc_device_ioctl+0x138/0xc60 [fastrpc] __arm64_sys_ioctl+0xa8/0xec invoke_syscall+0x48/0x114 el0_svc_common.constprop.0+0xd4/0xfc do_el0_svc+0x28/0x90 el0_svc+0x3c/0x130 el0t_64_sync_handler+0xa4/0x130 el0t_64_sync+0x18c/0x190 Code: 14000016 f94000a5 eb05029f 54000260 (b94018a6) ---[ end trace 0000000000000000 ]---

Cc: stable@vger.kernel.org Fixes: 5c1b97c7d7b7 ("misc: fastrpc: add support for FASTRPC_IOCTL_MEM_MAP/UNMAP") Reported-by: Jan Jablonsky jjablonsky@snapchat.com Signed-off-by: Srinivas Kandagatla srinivas.kandagatla@linaro.org --- drivers/misc/fastrpc.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c index 4bdc8e0df657..93ebd174d848 100644 --- a/drivers/misc/fastrpc.c +++ b/drivers/misc/fastrpc.c @@ -1748,17 +1748,18 @@ static int fastrpc_req_mmap(struct fastrpc_user *fl, char __user *argp) static int fastrpc_req_mem_unmap_impl(struct fastrpc_user *fl, struct fastrpc_mem_unmap *req) { struct fastrpc_invoke_args args[1] = { [0] = { 0 } }; - struct fastrpc_map *map = NULL, *m; + struct fastrpc_map *map = NULL, *iter, *m; struct fastrpc_mem_unmap_req_msg req_msg = { 0 }; int err = 0; u32 sc; struct device *dev = fl->sctx->dev;

spin_lock(&fl->lock); - list_for_each_entry_safe(map, m, &fl->maps, node) { - if ((req->fd < 0 || map->fd == req->fd) && (map->raddr == req->vaddr)) + list_for_each_entry_safe(iter, m, &fl->maps, node) { + if ((req->fd < 0 || iter->fd == req->fd) && (iter->raddr == req->vaddr)) { + map = iter; break; - map = NULL; + } }

spin_unlock(&fl->lock);