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It only deleted the list entry after the remote unmap succeeded. Two threads can therefore find the same entry and unmap it twice. That can lead to a double list deletion and double free. Detach the entry before invoking the DSP. Put it back if the remote unmap fails. Signed-off-by: Yousef Alhouseen --- drivers/misc/fastrpc.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c index ba4ade874..6a5239b1c 100644 --- a/drivers/misc/fastrpc.c +++ b/drivers/misc/fastrpc.c @@ -1902,7 +1902,8 @@ static int fastrpc_req_munmap_impl(struct fastrpc_user *fl, struct fastrpc_buf * if (!err) { dev_dbg(dev, "unmmap\tpt 0x%09lx OK\n", buf->raddr); spin_lock(&fl->lock); - list_del(&buf->node); + if (!list_empty(&buf->node)) + list_del_init(&buf->node); spin_unlock(&fl->lock); fastrpc_buf_free(buf); } else { @@ -1917,6 +1918,7 @@ static int fastrpc_req_munmap(struct fastrpc_user *fl, char __user *argp) struct fastrpc_buf *buf = NULL, *iter, *b; struct fastrpc_req_munmap req; struct device *dev = fl->sctx->dev; + int err; if (copy_from_user(&req, argp, sizeof(req))) return -EFAULT; @@ -1925,6 +1927,7 @@ static int fastrpc_req_munmap(struct fastrpc_user *fl, char __user *argp) list_for_each_entry_safe(iter, b, &fl->mmaps, node) { if ((iter->raddr == req.vaddrout) && (iter->size == req.size)) { buf = iter; + list_del_init(&buf->node); break; } } @@ -1936,7 +1939,14 @@ static int fastrpc_req_munmap(struct fastrpc_user *fl, char __user *argp) return -EINVAL; } - return fastrpc_req_munmap_impl(fl, buf); + err = fastrpc_req_munmap_impl(fl, buf); + if (err) { + spin_lock(&fl->lock); + list_add_tail(&buf->node, &fl->mmaps); + spin_unlock(&fl->lock); + } + + return err; } static int fastrpc_req_mmap(struct fastrpc_user *fl, char __user *argp) -- 2.54.0