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a0456399fb
The "Extended Compat ID OS Feature Descriptor Specification" does not
require the (sub)compatible ids to be NUL-terminated, because they
are placed in a fixed-size buffer and only unused parts of it should
contain NULs. If the buffer is fully utilized, there is no place for NULs.
Consequently, the code which uses desc->ext_compat_id never expects the
data contained to be NUL terminated.
If the compatible id is stored after sub-compatible id, and the compatible
id is full length (8 bytes), the (useless) NUL terminator overwrites the
first byte of the sub-compatible id.
If the sub-compatible id is full length (8 bytes), the (useless) NUL
terminator ends up out of the buffer. The situation can happen in the RNDIS
function, where the buffer is a part of struct f_rndis_opts. The next
member of struct f_rndis_opts is a mutex, so its first byte gets
overwritten. The said byte is a part of a mutex'es member which contains
the information on whether the muext is locked or not. This can lead to a
deadlock, because, in a configfs-composed gadget when a function is linked
into a configuration with config_usb_cfg_link(), usb_get_function()
is called, which then calls rndis_alloc(), which tries locking the same
mutex and (wrongly) finds it already locked.
This patch eliminates NUL terminating of the (sub)compatible id.
Cc: <stable@vger.kernel.org> # v3.16+
Fixes:
|
||
|---|---|---|
| .. | ||
| function | ||
| legacy | ||
| udc | ||
| composite.c | ||
| config.c | ||
| configfs.c | ||
| configfs.h | ||
| epautoconf.c | ||
| functions.c | ||
| Kconfig | ||
| Makefile | ||
| u_f.c | ||
| u_f.h | ||
| u_os_desc.h | ||
| usbstring.c | ||