From: Ekansh Gupta Date: Fri, 24 Jul 2026 22:33:38 +0000 (+0100) Subject: misc: fastrpc: Remove buffer from list prior to unmap operation X-Git-Tag: v7.2-rc7~8^2~13 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=6102ceb4eab845743ee57acd3863fbd06e93c927;p=thirdparty%2Flinux.git misc: fastrpc: Remove buffer from list prior to unmap operation fastrpc_req_munmap_impl() is called to unmap any buffer. The buffer is getting removed from the list after it is unmapped from DSP. This can create potential race conditions if multiple threads invoke unmap concurrently, where one thread may remove the entry from the list while another thread's unmap operation is still ongoing. Fix this by removing the buffer entry from the list before calling the unmap operation. If the unmap fails, the entry is re-added to the list so that userspace can retry the unmap, or alternatively, the buffer will be cleaned up during device release when the DSP process is torn down and all DSP-side mappings are freed along with remaining buffers in the list. Fixes: 2419e55e532de ("misc: fastrpc: add mmap/unmap support") Cc: stable@kernel.org Reviewed-by: Dmitry Baryshkov Signed-off-by: Ekansh Gupta Signed-off-by: Jianping Li Signed-off-by: Srinivas Kandagatla Link: https://patch.msgid.link/20260724223342.629168-3-srini@kernel.org Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c index 4f01ebfa6f95..12dcd2e737c3 100644 --- a/drivers/misc/fastrpc.c +++ b/drivers/misc/fastrpc.c @@ -1889,9 +1889,6 @@ static int fastrpc_req_munmap_impl(struct fastrpc_user *fl, struct fastrpc_buf * &args[0]); if (!err) { dev_dbg(dev, "unmmap\tpt 0x%09lx OK\n", buf->raddr); - spin_lock(&fl->lock); - list_del(&buf->node); - spin_unlock(&fl->lock); fastrpc_buf_free(buf); } else { dev_err(dev, "unmmap\tpt 0x%09lx ERROR\n", buf->raddr); @@ -1905,6 +1902,7 @@ 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; @@ -1912,6 +1910,7 @@ static int fastrpc_req_munmap(struct fastrpc_user *fl, char __user *argp) spin_lock(&fl->lock); list_for_each_entry_safe(iter, b, &fl->mmaps, node) { if ((iter->raddr == req.vaddrout) && (iter->size == req.size)) { + list_del(&iter->node); buf = iter; break; } @@ -1924,7 +1923,14 @@ 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)