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Jinchao Wang
e2b2740f12
commitd5e5cd3654upstream. dummy_hcd embeds a single shared usb_request (dum->fifo_req) that the "emulated single-request FIFO" fast-path in dummy_queue() reuses for small IN transfers: it copies the caller's request into it (req->req = *_req) and queues it, treating list_empty(&fifo_req.queue) as "the slot is free". The completion side (dummy_timer/transfer/nuke/dummy_dequeue) follows the standard pattern: list_del_init(&req->queue) unlinks the request, then the lock is dropped and usb_gadget_giveback_request() invokes req->complete(). But list_del_init() makes fifo_req.queue look empty *before* the completion callback returns, so a concurrent dummy_queue() on another CPU sees the slot as free, reuses fifo_req and runs req->req = *_req -- overwriting req->complete while dummy_timer is mid-calling it. The indirect call then jumps to a clobbered pointer, causing a general protection fault / page fault in dummy_timer (syzkaller extid faf3a6cf579fc65591ca). The clobbering write is an in-bounds memcpy on a live shared object, so KASAN cannot flag it. Add a fifo_req_busy bit covering the shared request's whole lifetime: set it in dummy_queue() when the FIFO fast-path takes fifo_req (making it the fast-path guard, replacing the list_empty(&fifo_req.queue) test), and clear it after the completion callback has returned, via a dummy_giveback() helper used at all four gadget-request giveback sites. The shared slot can no longer be reused until its completion callback has finished. Reported-by: syzbot+faf3a6cf579fc65591ca@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=faf3a6cf579fc65591ca Fixes:1da177e4c3("Linux-2.6.12-rc2") Cc: stable <stable@kernel.org> Signed-off-by: Jinchao Wang <wangjinchao600@gmail.com> Reviewed-by: Alan Stern <stern@rowland.harvard.edu> Link: https://patch.msgid.link/5db8bba5b3499a86cd2e776f9918126b68b2508b.1784198306.git.wangjinchao600@gmail.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.