linux/drivers/base/firmware_class.c, branch v4.11

firmware: fix NULL pointer dereference in __fw_load_abort()

2017-01-27T08:19:48Z

Since commit 5d47ec02c37ea6 ("firmware: Correct handling of fw_state_wait() return value") fw_load_abort() could be called twice and lead us to a kernel crash. This happens only when the firmware fallback mechanism (regular or custom) is used. The fallback mechanism exposes a sysfs interface for userspace to upload a file and notify the kernel when the file is loaded and ready, or to cancel an upload by echo'ing -1 into on the loading file: echo -n "-1" > /sys/$DEVPATH/loading This will call fw_load_abort(). Some distributions actually have a udev rule in place to *always* immediately cancel all firmware fallback mechanism requests (Debian), they have: $ cat /lib/udev/rules.d/50-firmware.rules # stub for immediately telling the kernel that userspace firmware loading # failed; necessary to avoid long timeouts with CONFIG_FW_LOADER_USER_HELPER=y SUBSYSTEM=="firmware", ACTION=="add", ATTR{loading}="-1 Distributions with this udev rule would run into this crash only if the fallback mechanism is used. Since most distributions disable by default using the fallback mechanism (CONFIG_FW_LOADER_USER_HELPER_FALLBACK), this would typicaly mean only 2 drivers which *require* the fallback mechanism could typically incur a crash: drivers/firmware/dell_rbu.c and the drivers/leds/leds-lp55xx-common.c driver. Distributions enabling CONFIG_FW_LOADER_USER_HELPER_FALLBACK by default are obviously more exposed to this crash. The crash happens because after commit 5b029624948d ("firmware: do not use fw_lock for fw_state protection") and subsequent fix commit 5d47ec02c37ea6 ("firmware: Correct handling of fw_state_wait() return value") a race can happen between this cancelation and the firmware fw_state_wait_timeout() being woken up after a state change with which fw_load_abort() as that calls swake_up(). Upon error fw_state_wait_timeout() will also again call fw_load_abort() and trigger a null reference. At first glance we could just fix this with a !buf check on fw_load_abort() before accessing buf->fw_st, however there is a logical issue in having a state machine used for the fallback mechanism and preventing access from it once we abort as its inside the buf (buf->fw_st). The firmware_class.c code is setting the buf to NULL to annotate an abort has occurred. Replace this mechanism by simply using the state check instead. All the other code in place already uses similar checks for aborting as well so no further changes are needed. An oops can be reproduced with the new fw_fallback.sh fallback mechanism cancellation test. Either cancelling the fallback mechanism or the custom fallback mechanism triggers a crash. mcgrof@piggy ~/linux-next/tools/testing/selftests/firmware (git::20170111-fw-fixes)$ sudo ./fw_fallback.sh ./fw_fallback.sh: timeout works ./fw_fallback.sh: firmware comparison works ./fw_fallback.sh: fallback mechanism works [ this then sits here when it is trying the cancellation test ] Kernel log: test_firmware: loading 'nope-test-firmware.bin' misc test_firmware: Direct firmware load for nope-test-firmware.bin failed with error -2 misc test_firmware: Falling back to user helper BUG: unable to handle kernel NULL pointer dereference at 0000000000000038 IP: _request_firmware+0xa27/0xad0 PGD 0 Oops: 0000 [#1] SMP Modules linked in: test_firmware(E) ... etc ... CPU: 1 PID: 1396 Comm: fw_fallback.sh Tainted: G W E 4.10.0-rc3-next-20170111+ #30 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.10.1-0-g8891697-prebuilt.qemu-project.org 04/01/2014 task: ffff9740b27f4340 task.stack: ffffbb15c0bc8000 RIP: 0010:_request_firmware+0xa27/0xad0 RSP: 0018:ffffbb15c0bcbd10 EFLAGS: 00010246 RAX: 00000000fffffffe RBX: ffff9740afe5aa80 RCX: 0000000000000000 RDX: ffff9740b27f4340 RSI: 0000000000000283 RDI: 0000000000000000 RBP: ffffbb15c0bcbd90 R08: ffffbb15c0bcbcd8 R09: 0000000000000000 R10: 0000000894a0d4b1 R11: 000000000000008c R12: ffffffffc0312480 R13: 0000000000000005 R14: ffff9740b1c32400 R15: 00000000000003e8 FS: 00007f8604422700(0000) GS:ffff9740bfc80000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000038 CR3: 000000012164c000 CR4: 00000000000006e0 Call Trace: request_firmware+0x37/0x50 trigger_request_store+0x79/0xd0 [test_firmware] dev_attr_store+0x18/0x30 sysfs_kf_write+0x37/0x40 kernfs_fop_write+0x110/0x1a0 __vfs_write+0x37/0x160 ? _cond_resched+0x1a/0x50 vfs_write+0xb5/0x1a0 SyS_write+0x55/0xc0 ? trace_do_page_fault+0x37/0xd0 entry_SYSCALL_64_fastpath+0x1e/0xad RIP: 0033:0x7f8603f49620 RSP: 002b:00007fff6287b788 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 000055c307b110a0 RCX: 00007f8603f49620 RDX: 0000000000000016 RSI: 000055c3084d8a90 RDI: 0000000000000001 RBP: 0000000000000016 R08: 000000000000c0ff R09: 000055c3084d6336 R10: 000055c307b108b0 R11: 0000000000000246 R12: 000055c307b13c80 R13: 000055c3084d6320 R14: 0000000000000000 R15: 00007fff6287b950 Code: 9f 64 84 e8 9c 61 fe ff b8 f4 ff ff ff e9 6b f9 ff ff 48 c7 c7 40 6b 8d 84 89 45 a8 e8 43 84 18 00 49 8b be 00 03 00 00 8b 45 a8 <83> 7f 38 02 74 08 e8 6e ec ff ff 8b 45 a8 49 c7 86 00 03 00 00 RIP: _request_firmware+0xa27/0xad0 RSP: ffffbb15c0bcbd10 CR2: 0000000000000038 ---[ end trace 6d94ac339c133e6f ]--- Fixes: 5d47ec02c37e ("firmware: Correct handling of fw_state_wait() return value") Reported-and-Tested-by: Jakub Kicinski Reported-and-Tested-by: Patrick Bruenn Reported-by: Chris Wilson CC: [3.10+] Signed-off-by: Luis R. Rodriguez Signed-off-by: Greg Kroah-Hartman

firmware: Correct handling of fw_state_wait() return value

2016-12-08T20:05:54Z

When request_firmware() finds an already open firmware object it will wait for that object to become fully loaded and then check the status. As __fw_state_wait_common() succeeds the timeout value returned will be truncated in _request_firmware_prepare() and interpreted as -EPERM. Prior to "firmware: do not use fw_lock for fw_state protection" the code did test if we where in the "done" state before sleeping, causing this particular code path to succeed, in some cases. As the callers are interested in the result of the wait and not the remaining timeout the return value of __fw_state_wait_common() is changed to signal "done" or "error", which simplifies the logic in _request_firmware_load() as well. Fixes: 5b029624948d ("firmware: do not use fw_lock for fw_state protection") Signed-off-by: Bjorn Andersson Reviewed-by: Daniel Wagner Acked-by: Luis R. Rodriguez Signed-off-by: Greg Kroah-Hartman

firmware: remove warning at documentation generation time

2016-12-01T20:41:13Z

This patch removes following error at for `make htmldocs`. No functional change. ./drivers/base/firmware_class.c:1348: WARNING: Bullet list ends without a blank line; unexpected unindent. Signed-off-by: Silvio Fricke Reviewed-by: Mauro Carvalho Chehab Acked-by: Luis R. Rodriguez Signed-off-by: Greg Kroah-Hartman

firmware: move fw_state_is_done() into UHM section

2016-11-29T20:28:54Z

fw_state_is_done() is only used for UHM so moved into that section. Cc: Ming Lei Signed-off-by: Daniel Wagner Acked-by: Luis R. Rodriguez Signed-off-by: Greg Kroah-Hartman

firmware: do not use fw_lock for fw_state protection

2016-11-29T20:28:54Z

fw_lock is to use to protect 'corner cases' inside firmware_class. It is not exactly clear what those corner cases are nor what it exactly protects. fw_state can be used without needing the fw_lock to protect its state transition and wake ups. fw_state is holds the state in status and the completion is used to wake up all waiters (in this case that is the user land helper so only one). This operation has to be 'atomic' to avoid races. We can do this by using swait which takes care we don't miss any wake up. We use also swait instead of wait because don't need all the additional features wait provides. Note there some more cleanups possible after with this change. For example for !CONFIG_FW_LOADER_USER_HELPER we don't check for the state anymore. Let's to this in the next patch instead mingling to many changes into this one. And yes you get a gcc warning "‘__fw_state_check’ defined but not used [-Wunused-function] code." for the time beeing. Cc: Ming Lei Signed-off-by: Daniel Wagner Acked-by: Luis R. Rodriguez Signed-off-by: Greg Kroah-Hartman

firmware: drop bit ops in favor of simple state machine

2016-11-29T20:28:54Z

We track the state of the firmware loading with bit ops. Since the state machine has only a few states and they are all mutual exclusive there are only a few simple state transition we can model this simplify. UNKNOWN -> LOADING -> DONE | ABORTED Because we don't use any bit ops on fw_state::status anymore we are able to change the data type to enum fw_status and update the function arguments accordingly. READ_ONCE() and WRITE_ONCE() are propably not needed because there are a lot of load and stores around fw_st->status. But let's make it explicit and not be sorry later. Cc: Ming Lei Signed-off-by: Daniel Wagner Acked-by: Luis R. Rodriguez Signed-off-by: Greg Kroah-Hartman

firmware: refactor loading status

2016-11-29T20:28:54Z

The firmware loader tracks the current state of the loading process via unsigned long status and a completion in struct firmware_buf. Instead of open code tracking the state, introduce data structure which encapsulate the state tracking and synchronization. While at it also separate UHM states from direct loading states, e.g. the loading_timeout is only defined when CONFIG_FW_LOADER_USER_HELPER. Cc: Ming Lei Signed-off-by: Daniel Wagner Acked-by: Luis R. Rodriguez Signed-off-by: Greg Kroah-Hartman

firmware: fix usermode helper fallback loading

2016-11-29T20:26:41Z

When you use the firmware usermode helper fallback with a timeout value set to a value greater than INT_MAX (2147483647) a cast overflow issue causes the timeout value to go negative and breaks all usermode helper loading. This regression was introduced through commit 68ff2a00dbf5 ("firmware_loader: handle timeout via wait_for_completion_interruptible_timeout()") on kernel v4.0. The firmware_class drivers relies on the firmware usermode helper fallback as a mechanism to look for firmware if the direct filesystem search failed only if: a) You've enabled CONFIG_FW_LOADER_USER_HELPER_FALLBACK (not many distros): Then all of these callers will rely on the fallback mechanism in case the firmware is not found through an initial direct filesystem lookup: o request_firmware() o request_firmware_into_buf() o request_firmware_nowait() b) If you've only enabled CONFIG_FW_LOADER_USER_HELPER (most distros): Then only callers using request_firmware_nowait() with the second argument set to false, this explicitly is requesting the UMH firmware fallback to be relied on in case the first filesystem lookup fails. Using Coccinelle SmPL grammar we have identified only two drivers explicitly requesting the UMH firmware fallback mechanism: - drivers/firmware/dell_rbu.c - drivers/leds/leds-lp55xx-common.c Since most distributions only enable CONFIG_FW_LOADER_USER_HELPER the biggest impact of this regression are users of the dell_rbu and leds-lp55xx-common device driver which required the UMH to find their respective needed firmwares. The default timeout for the UMH is set to 60 seconds always, as of commit 68ff2a00dbf5 ("firmware_loader: handle timeout via wait_for_completion_interruptible_timeout()") the timeout was bumped to MAX_JIFFY_OFFSET ((LONG_MAX >> 1)-1). Additionally the MAX_JIFFY_OFFSET value was also used if the timeout was configured by a user to 0. The following works: echo 2147483647 > /sys/class/firmware/timeout But both of the following set the timeout to MAX_JIFFY_OFFSET even if we display 0 back to userspace: echo 2147483648 > /sys/class/firmware/timeout cat /sys/class/firmware/timeout 0 echo 0> /sys/class/firmware/timeout cat /sys/class/firmware/timeout 0 A max value of INT_MAX (2147483647) seconds is therefore implicit due to the another cast with simple_strtol(). This fixes the secondary cast (the first one is simple_strtol() but its an issue only by forcing an implicit limit) by re-using the timeout variable and only setting retval in appropriate cases. Lastly worth noting systemd had ripped out the UMH firmware fallback mechanism from udev since udev 2014 via commit be2ea723b1d023b3d ("udev: remove userspace firmware loading support"), so as of systemd v217. Signed-off-by: Yves-Alexis Perez Fixes: 68ff2a00dbf5 "firmware_loader: handle timeout via wait_for_completion_interruptible_timeout()" Cc: Luis R. Rodriguez Cc: Ming Lei Cc: Bjorn Andersson Cc: Greg Kroah-Hartman Cc: stable@vger.kernel.org Acked-by: Luis R. Rodriguez Reviewed-by: Bjorn Andersson [mcgrof@kernel.org: gave commit log a whole lot of love] Signed-off-by: Luis R. Rodriguez Signed-off-by: Greg Kroah-Hartman

driver core: firmware_class: convert to use class_groups

2016-11-29T20:12:12Z

Convert the firmware core to use class_groups instead of class_attrs as that's the correct way to handle lists of class attribute files. Cc: Ming Lei Acked-by: Luis R. Rodriguez Signed-off-by: Greg Kroah-Hartman

firmware: support loading into a pre-allocated buffer

2016-08-02T23:35:10Z

Some systems are memory constrained but they need to load very large firmwares. The firmware subsystem allows drivers to request this firmware be loaded from the filesystem, but this requires that the entire firmware be loaded into kernel memory first before it's provided to the driver. This can lead to a situation where we map the firmware twice, once to load the firmware into kernel memory and once to copy the firmware into the final resting place. This creates needless memory pressure and delays loading because we have to copy from kernel memory to somewhere else. Let's add a request_firmware_into_buf() API that allows drivers to request firmware be loaded directly into a pre-allocated buffer. This skips the intermediate step of allocating a buffer in kernel memory to hold the firmware image while it's read from the filesystem. It also requires that drivers know how much memory they'll require before requesting the firmware and negates any benefits of firmware caching because the firmware layer doesn't manage the buffer lifetime. For a 16MB buffer, about half the time is spent performing a memcpy from the buffer to the final resting place. I see loading times go from 0.081171 seconds to 0.047696 seconds after applying this patch. Plus the vmalloc pressure is reduced. This is based on a patch from Vikram Mulukutla on codeaurora.org: https://www.codeaurora.org/cgit/quic/la/kernel/msm-3.18/commit/drivers/base/firmware_class.c?h=rel/msm-3.18&id=0a328c5f6cd999f5c591f172216835636f39bcb5 Link: http://lkml.kernel.org/r/20160607164741.31849-4-stephen.boyd@linaro.org Signed-off-by: Stephen Boyd Cc: Mimi Zohar Cc: Vikram Mulukutla Cc: Mark Brown Cc: Ming Lei Cc: Greg Kroah-Hartman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds