user/sven/linux.git/kernel/taskstats.c, branch v3.0.67

Make TASKSTATS require root access

2011-12-21T20:57:40Z

commit 1a51410abe7d0ee4b1d112780f46df87d3621043 upstream. Ok, this isn't optimal, since it means that 'iotop' needs admin capabilities, and we may have to work on this some more. But at the same time it is very much not acceptable to let anybody just read anybody elses IO statistics quite at this level. Use of the GENL_ADMIN_PERM suggested by Johannes Berg as an alternative to checking the capabilities by hand. Reported-by: Vasiliy Kulikov Cc: Johannes Berg Acked-by: Balbir Singh Signed-off-by: Linus Torvalds Cc: Moritz Mühlenhoff Signed-off-by: Greg Kroah-Hartman

taskstats: don't allow duplicate entries in listener mode

2011-06-28T01:00:13Z

Currently a single process may register exit handlers unlimited times. It may lead to a bloated listeners chain and very slow process terminations. Eg after 10KK sent TASKSTATS_CMD_ATTR_REGISTER_CPUMASKs ~300 Mb of kernel memory is stolen for the handlers chain and "time id" shows 2-7 seconds instead of normal 0.003. It makes it possible to exhaust all kernel memory and to eat much of CPU time by triggerring numerous exits on a single CPU. The patch limits the number of times a single process may register itself on a single CPU to one. One little issue is kept unfixed - as taskstats_exit() is called before exit_files() in do_exit(), the orphaned listener entry (if it was not explicitly deregistered) is kept until the next someone's exit() and implicit deregistration in send_cpu_listeners(). So, if a process registered itself as a listener exits and the next spawned process gets the same pid, it would inherit taskstats attributes. Signed-off-by: Vasiliy Kulikov Cc: Balbir Singh Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

taskstats: use appropriate printk priority level

2011-03-24T02:47:14Z

printk()s without a priority level default to KERN_WARNING. To reduce noise at KERN_WARNING, this patch set the priority level appriopriately for unleveled printks()s. This should be useful to folks that look at dmesg warnings closely. Signed-off-by: Mandeep Singh Baines Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

taskstats: use better ifdef for alignment

2011-01-13T16:03:19Z

Commit 4be2c95d ("taskstats: pad taskstats netlink response for aligment issues on ia64") added a null field to align the taskstats structure but the discussion centered around ia64. The issue exists on other platforms with inefficient unaligned access and adding them piecemeal would be an unmaintainable mess. This patch uses Dave Miller's suggestion of using a combination of CONFIG_64BIT && !CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS to determine whether alignment is needed. Note that this will cause breakage on those platforms with applications like iotop which had hard-coded offsets into the packet to access the taskstats structure. The message seen on systems without the alignment fixes looks like: kernel unaligned access to 0xe000023879dca9bc, ip=0xa000000100133d10 The addresses may vary but resolve to locations inside __delayacct_add_tsk. iotop makes what I'd call unreasonable assumptions about the contents of a netlink genetlink packet containing generic attributes. They're typed and have headers that specify value lengths, so the client can (should) identify and skip the ones the client doesn't understand. The kernel, as of version 2.6.36, presented a packet like so: +--------------------------------+ | genlmsghdr - 4 bytes | +--------------------------------+ | NLA header - 4 bytes | /* Aggregate header */ +-+------------------------------+ | | NLA header - 4 bytes | /* PID header */ | +------------------------------+ | | pid/tgid - 4 bytes | | +------------------------------+ | | NLA header - 4 bytes | /* stats header */ | + -----------------------------+ <- oops. aligned on 4 byte boundary | | struct taskstats - 328 bytes | +-+------------------------------+ The iotop code expects that the kernel will behave as it did then, assuming that the packet format is set in stone. The format is set in stone, but the packet offsets are not. There's nothing in the packet format that guarantees that the packet will be sent in exactly the same way. The attribute contents are set (or versioned) and the aggregate contents are set but they can be anywhere in the packet. The issue here isn't that an unaligned structure gets passed to userspace, it's that the NLA infrastructure has something of a weakness: The 4 byte attribute header may force the payload to be unaligned. The taskstats structure is created at an unaligned location and then 64-bit values are operated on inside the kernel, so the unaligned access warnings gets spewed everywhere. It's possible to use the unaligned access API to operate on the structure in the kernel but it seems like a wasted effort to work around userspace code that isn't following the packet format. Any new additions would also need the be worked around. It's a maintenance nightmare. The conclusion of the earlier discussion seemed to be "ok fine, if we have to break it, don't break it on arches that don't have the problem." Dave pointed out that the unaligned access problem doesn't only exist on ia64, but also on other 64-bit arches that don't have efficient unaligned access and it should be fixed there as well. The committed version of the patch and this addition keep with the conclusion of that discussion not to break it unnecessarily, which the pid padding and the packet padding fixes did do. x86_64 and powerpc don't suffer this problem so they shouldn't suffer the solution. Other 64-bit architectures do and will, though. Signed-off-by: Jeff Mahoney Reported-by: David S. Miller Acked-by: David S. Miller Cc: Dan Carpenter Cc: Balbir Singh Cc: Florian Mickler Cc: Guillaume Chazarain Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Merge branch 'for-2.6.38' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu

2011-01-08T01:02:58Z

* 'for-2.6.38' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu: (30 commits) gameport: use this_cpu_read instead of lookup x86: udelay: Use this_cpu_read to avoid address calculation x86: Use this_cpu_inc_return for nmi counter x86: Replace uses of current_cpu_data with this_cpu ops x86: Use this_cpu_ops to optimize code vmstat: User per cpu atomics to avoid interrupt disable / enable irq_work: Use per cpu atomics instead of regular atomics cpuops: Use cmpxchg for xchg to avoid lock semantics x86: this_cpu_cmpxchg and this_cpu_xchg operations percpu: Generic this_cpu_cmpxchg() and this_cpu_xchg support percpu,x86: relocate this_cpu_add_return() and friends connector: Use this_cpu operations xen: Use this_cpu_inc_return taskstats: Use this_cpu_ops random: Use this_cpu_inc_return fs: Use this_cpu_inc_return in buffer.c highmem: Use this_cpu_xx_return() operations vmstat: Use this_cpu_inc_return for vm statistics x86: Support for this_cpu_add, sub, dec, inc_return percpu: Generic support for this_cpu_add, sub, dec, inc_return ... Fixed up conflicts: in arch/x86/kernel/{apic/nmi.c, apic/x2apic_uv_x.c, process.c} as per Tejun.

taskstats: pad taskstats netlink response for aligment issues on ia64

2010-12-23T03:43:34Z

The taskstats structure is internally aligned on 8 byte boundaries but the layout of the aggregrate reply, with two NLA headers and the pid (each 4 bytes), actually force the entire structure to be unaligned. This causes the kernel to issue unaligned access warnings on some architectures like ia64. Unfortunately, some software out there doesn't properly unroll the NLA packet and assumes that the start of the taskstats structure will always be 20 bytes from the start of the netlink payload. Aligning the start of the taskstats structure breaks this software, which we don't want. So, for now the alignment only happens on architectures that require it and those users will have to update to fixed versions of those packages. Space is reserved in the packet only when needed. This ifdef should be removed in several years e.g. 2012 once we can be confident that fixed versions are installed on most systems. We add the padding before the aggregate since the aggregate is already a defined type. Commit 85893120 ("delayacct: align to 8 byte boundary on 64-bit systems") previously addressed the alignment issues by padding out the pid field. This was supposed to be a compatible change but the circumstances described above mean that it wasn't. This patch backs out that change, since it was a hack, and introduces a new NULL attribute type to provide the padding. Padding the response with 4 bytes avoids allocating an aligned taskstats structure and copying it back. Since the structure weighs in at 328 bytes, it's too big to do it on the stack. Signed-off-by: Jeff Mahoney Reported-by: Brian Rogers Cc: Jeff Mahoney Cc: Guillaume Chazarain Cc: Balbir Singh Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

taskstats: Use this_cpu_ops

2010-12-17T14:18:05Z

Use this_cpu_inc_return in one place and avoid ugly __raw_get_cpu in another. V3->V4: - Fix off by one. V4-V4f: - Use &listener_array Cc: Michael Holzheu Acked-by: H. Peter Anvin Signed-off-by: Christoph Lameter Signed-off-by: Tejun Heo

taskstats: split fill_pid function

2010-10-28T01:03:17Z

Separate the finding of a task_struct by pid or tgid from filling the taskstats data. This makes the code more readable. Signed-off-by: Michael Holzheu Acked-by: Balbir Singh Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

taskstats: separate taskstats commands

2010-10-28T01:03:17Z

Move each taskstats command into a single function. This makes the code more readable and makes it easier to add new commands. Signed-off-by: Michael Holzheu Acked-by: Balbir Singh Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

delayacct: align to 8 byte boundary on 64-bit systems

2010-10-28T01:03:17Z

prepare_reply() sets up an skb for the response. The payload contains: +--------------------------------+ | genlmsghdr - 4 bytes | +--------------------------------+ | NLA header - 4 bytes | /* Aggregate header */ +-+------------------------------+ | | NLA header - 4 bytes | /* PID header */ | +------------------------------+ | | pid/tgid - 4 bytes | | +------------------------------+ | | NLA header - 4 bytes | /* stats header */ | + -----------------------------+ <- oops. aligned on 4 byte boundary | | struct taskstats - 328 bytes | +-+------------------------------+ The start of the taskstats struct must be 8 byte aligned on IA64 (and other systems with 8 byte alignment rules for 64-bit types) or runtime alignment warnings will be issued. This patch pads the pid/tgid field out to sizeof(long), which forces the alignment of taskstats. The getdelays userspace code is ok with this since it assumes 32-bit pid/tgid and then honors that header's length field. An array is used to avoid exposing kernel memory contents to userspace in the response. Signed-off-by: Jeff Mahoney Cc: Balbir Singh Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds