BMC/Intel-BMC/linux.git/include/linux/kmod.h, branch v3.3

PM / Sleep: Fix freezer failures due to racy usermodehelper_is_disabled()

2011-12-09T22:36:36+00:00

Commit a144c6a (PM: Print a warning if firmware is requested when tasks are frozen) introduced usermodehelper_is_disabled() to warn and exit immediately if firmware is requested when usermodehelpers are disabled. However, it is racy. Consider the following scenario, currently used in drivers/base/firmware_class.c: ... if (usermodehelper_is_disabled()) goto out; /* Do actual work */ ... out: return err; Nothing prevents someone from disabling usermodehelpers just after the check in the 'if' condition, which means that it is quite possible to try doing the "actual work" with usermodehelpers disabled, leading to undesirable consequences. In particular, this race condition in _request_firmware() causes task freezing failures whenever suspend/hibernation is in progress because, it wrongly waits to get the firmware/microcode image from userspace when actually the usermodehelpers are disabled or userspace has been frozen. Some of the example scenarios that cause freezing failures due to this race are those that depend on userspace via request_firmware(), such as x86 microcode module initialization and microcode image reload. Previous discussions about this issue can be found at: http://thread.gmane.org/gmane.linux.kernel/1198291/focus=1200591 This patch adds proper synchronization to fix this issue. It is to be noted that this patchset fixes the freezing failures but doesn't remove the warnings. IOW, it does not attempt to add explicit synchronization to x86 microcode driver to avoid requesting microcode image at inopportune moments. Because, the warnings were introduced to highlight such cases, in the first place. And we need not silence the warnings, since we take care of the *real* problem (freezing failure) and hence, after that, the warnings are pretty harmless anyway. Signed-off-by: Srivatsa S. Bhat Signed-off-by: Rafael J. Wysocki

treewide: use printf not attribute__((format(printf,...)))

2011-11-01T00:30:54+00:00

Standardize the style for compiler based printf format verification. Standardized the location of __printf too. Done via script and a little typing. $ grep -rPl --include=*.[ch] -w "__attribute__" * | \ grep -vP "^(tools|scripts|include/linux/compiler-gcc.h)" | \ xargs perl -n -i -e 'local $/; while (<>) { s/\b__attribute__\s*$\s*\(\s*format\s*\(\s*printf\s*,\s*(.+)\s*,\s*(.+)\s*$\s*\)\s*\)/__printf($1, $2)/g ; print; }' [akpm@linux-foundation.org: revert arch bits] Signed-off-by: Joe Perches Cc: "Kirill A. Shutemov" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

KEYS/DNS: Fix ____call_usermodehelper() to not lose the session keyring

2011-06-17T16:40:48+00:00

____call_usermodehelper() now erases any credentials set by the subprocess_inf::init() function. The problem is that commit 17f60a7da150 ("capabilites: allow the application of capability limits to usermode helpers") creates and commits new credentials with prepare_kernel_cred() after the call to the init() function. This wipes all keyrings after umh_keys_init() is called. The best way to deal with this is to put the init() call just prior to the commit_creds() call, and pass the cred pointer to init(). That means that umh_keys_init() and suchlike can modify the credentials _before_ they are published and potentially in use by the rest of the system. This prevents request_key() from working as it is prevented from passing the session keyring it set up with the authorisation token to /sbin/request-key, and so the latter can't assume the authority to instantiate the key. This causes the in-kernel DNS resolver to fail with ENOKEY unconditionally. Signed-off-by: David Howells Acked-by: Eric Paris Tested-by: Jeff Layton Signed-off-by: Linus Torvalds

Merge branch 'next' into for-linus

2011-05-24T12:55:24+00:00

kmod: always provide usermodehelper_disable()

2011-05-17T21:19:18+00:00

We need to prevent kernel-forked processes during system poweroff. Such processes try to access the filesystem whose disks we are trying to shutdown at the same time. This causes delays and exceptions in the storage drivers. A follow-up patch will add these calls and need usermodehelper_disable() also on systems without suspend support. Signed-off-by: Kay Sievers Signed-off-by: Rafael J. Wysocki

PM: Print a warning if firmware is requested when tasks are frozen

2011-05-17T21:19:17+00:00

Some drivers erroneously use request_firmware() from their ->resume() (or ->thaw(), or ->restore()) callbacks, which is not going to work unless the firmware has been built in. This causes system resume to stall until the firmware-loading timeout expires, which makes users think that the resume has failed and reboot their machines unnecessarily. For this reason, make _request_firmware() print a warning and return immediately with error code if it has been called when tasks are frozen and it's impossible to start any new usermode helpers. Signed-off-by: Rafael J. Wysocki Acked-by: Greg Kroah-Hartman Reviewed-by: Valdis Kletnieks

capabilites: allow the application of capability limits to usermode helpers

2011-04-04T00:31:04+00:00

There is no way to limit the capabilities of usermodehelpers. This problem reared its head recently when someone complained that any user with cap_net_admin was able to load arbitrary kernel modules, even though the user didn't have cap_sys_module. The reason is because the actual load is done by a usermode helper and those always have the full cap set. This patch addes new sysctls which allow us to bound the permissions of usermode helpers. /proc/sys/kernel/usermodehelper/bset /proc/sys/kernel/usermodehelper/inheritable You must have CAP_SYS_MODULE and CAP_SETPCAP to change these (changes are &= ONLY). When the kernel launches a usermodehelper it will do so with these as the bset and pI. -v2: make globals static create spinlock to protect globals -v3: require both CAP_SETPCAP and CAP_SYS_MODULE -v4: fix the typo s/CAP_SET_PCAP/CAP_SETPCAP/ because I didn't commit Signed-off-by: Eric Paris No-objection-from: Serge E. Hallyn Acked-by: David Howells Acked-by: Serge E. Hallyn Acked-by: Andrew G. Morgan Signed-off-by: James Morris

umh: creds: kill subprocess_info->cred logic

2010-05-27T16:12:45+00:00

Now that nobody ever changes subprocess_info->cred we can kill this member and related code. ____call_usermodehelper() always runs in the context of freshly forked kernel thread, it has the proper ->cred copied from its parent kthread, keventd. Signed-off-by: Oleg Nesterov Acked-by: Neil Horman Acked-by: David Howells Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

umh: creds: convert call_usermodehelper_keys() to use subprocess_info->init()

2010-05-27T16:12:45+00:00

call_usermodehelper_keys() uses call_usermodehelper_setkeys() to change subprocess_info->cred in advance. Now that we have info->init() we can change this code to set tgcred->session_keyring in context of execing kernel thread. Note: since currently call_usermodehelper_keys() is never called with UMH_NO_WAIT, call_usermodehelper_keys()->key_get() and umh_keys_cleanup() are not really needed, we could rely on install_session_keyring_to_cred() which does key_get() on success. Signed-off-by: Oleg Nesterov Acked-by: Neil Horman Acked-by: David Howells Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

exec: replace call_usermodehelper_pipe with use of umh init function and resolve limit

2010-05-27T16:12:44+00:00

The first patch in this series introduced an init function to the call_usermodehelper api so that processes could be customized by caller. This patch takes advantage of that fact, by customizing the helper in do_coredump to create the pipe and set its core limit to one (for our recusrsion check). This lets us clean up the previous uglyness in the usermodehelper internals and factor call_usermodehelper out entirely. While I'm at it, we can also modify the helper setup to look for a core limit value of 1 rather than zero for our recursion check Signed-off-by: Neil Horman Reviewed-by: Oleg Nesterov Cc: Andi Kleen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

BMC/Intel-BMC/linux.git/include/linux/kmod.h, branch v3.3

PM / Sleep: Fix freezer failures due to racy usermodehelper_is_disabled()

treewide: use __printf not __attribute__((format(printf,...)))

KEYS/DNS: Fix ____call_usermodehelper() to not lose the session keyring

Merge branch 'next' into for-linus

kmod: always provide usermodehelper_disable()

PM: Print a warning if firmware is requested when tasks are frozen

capabilites: allow the application of capability limits to usermode helpers

umh: creds: kill subprocess_info->cred logic

umh: creds: convert call_usermodehelper_keys() to use subprocess_info->init()

exec: replace call_usermodehelper_pipe with use of umh init function and resolve limit

treewide: use printf not attribute__((format(printf,...)))