From 8bdcf96eb135aebacac319667f87db034fb38406 Mon Sep 17 00:00:00 2001 From: Neill Kapron Date: Fri, 19 Jun 2026 04:06:04 +0000 Subject: [PATCH] usb: gadget: f_fs: Tie read_buffer lifetime to ffs_epfile MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Currently, ffs_epfile_release unconditionally frees the endpoint's read_buffer when a file descriptor is closed. If userspace explicitly opens the endpoint multiple times and closes one, the read_buffer is destroyed. This can lead to silent data loss if other file descriptors are still actively reading from the endpoint. By tying the lifetime of the read_buffer to the ffs_epfile structure itself (which is destroyed when the functionfs instance is torn down in ffs_epfiles_destroy), we eliminate the brittle dependency on open/release calls while correctly matching the conceptual lifetime of unread data on the hardware endpoint. Fixes: 9353afbbfa7b ("usb: gadget: f_fs: buffer data from ‘oversized’ OUT requests") Cc: stable Assisted-by: Antigravity:gemini-3.1-pro Signed-off-by: Neill Kapron Link: https://patch.msgid.link/20260619040609.4010746-3-nkapron@google.com Signed-off-by: Greg Kroah-Hartman --- drivers/usb/gadget/function/f_fs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c index d9b95fb830df..44218be1e676 100644 --- a/drivers/usb/gadget/function/f_fs.c +++ b/drivers/usb/gadget/function/f_fs.c @@ -1375,7 +1375,6 @@ ffs_epfile_release(struct inode *inode, struct file *file) mutex_unlock(&epfile->dmabufs_mutex); - __ffs_epfile_read_buffer_free(epfile); ffs_data_closed(epfile->ffs); return 0; @@ -2393,6 +2392,7 @@ static void ffs_epfiles_destroy(struct super_block *sb, for (; count; --count, ++epfile) { BUG_ON(mutex_is_locked(&epfile->mutex)); + __ffs_epfile_read_buffer_free(epfile); simple_remove_by_name(root, epfile->name, clear_one); }