Commit b4cbb197c7 ("vm: add vm_iomap_memory() helper function") added
a helper function wrapper around io_remap_pfn_range(), and every other
architecture defined it in <asm/pgtable.h>.
The s390 choice of <asm/io.h> may make sense, but is not very convenient
for this case, and gratuitous differences like that cause unexpected errors like this:
mm/memory.c: In function 'vm_iomap_memory':
mm/memory.c:2439:2: error: implicit declaration of function 'io_remap_pfn_range' [-Werror=implicit-function-declaration]
Glory be the kbuild test robot who noticed this, bisected it, and
reported it to the guilty parties (ie me).
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Using this parameter one can disable the storage_size/2 check if
he is really sure that the UEFI does sane gc and fulfills the spec.
This parameter is useful if a devices uses more than 50% of the
storage by default.
The Intel DQSW67 desktop board is such a sucker for exmaple.
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
Commit 7e98d53086 (Synchronize fuse header with
one used in library) added #ifdef __linux__ around defines if it is not set.
The kernel build is self-contained and can be built on non-Linux toolchains.
After the mentioned commit builds on non-Linux toolchains will try to include
stdint.h and fail due to -nostdinc, and then fail with a bunch of undefined type
errors.
Fix by checking for __KERNEL__ instead of __linux__ and using the standard int
types instead of the linux specific ones.
Reported-by: Arve Hjønnevåg <arve@android.com>
Reported-by: Colin Cross <ccross@android.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
o Commit 319ecf121e
("qlcnic: 83xx sysfs routines") introduced regression
for beaconing test while refactoring 82xx code. This patch is to
revert code to fix beaconing test for 82xx adapter.
Signed-off-by: Himanshu Madhani <himanshu.madhani@qlogic.com>
Signed-off-by: Shahed Shaikh <shahed.shaikh@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Commit 4a94445c9a (net: Use ip_route_input_noref() in input path)
added a bug in IP defragmentation handling, as non refcounted
dst could escape an RCU protected section.
Commit 64f3b9e203 (net: ip_expire() must revalidate route) fixed
the case of timeouts, but not the general problem.
Tom Parkin noticed crashes in UDP stack and provided a patch,
but further analysis permitted us to pinpoint the root cause.
Before queueing a packet into a frag list, we must drop its dst,
as this dst has limited lifetime (RCU protected)
When/if a packet is finally reassembled, we use the dst of the very
last skb, still protected by RCU and valid, as the dst of the
reassembled packet.
Use same logic in IPv6, as there is no need to hold dst references.
Reported-by: Tom Parkin <tparkin@katalix.com>
Tested-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Pull ARM fix from Russell King:
"A build fix for an incomplete change to the ARM cpu suspend code"
* branch 'fixes' of git://git.linaro.org/people/rmk/linux-arm:
ARM: Do 15e0d9e37c (ARM: pm: let platforms select cpu_suspend support) properly
Pull kvm fixes from Marcelo Tosatti:
"PPC and ARM KVM fixes"
* git://git.kernel.org/pub/scm/virt/kvm/kvm:
ARM: KVM: fix L_PTE_S2_RDWR to actually be Read/Write
ARM: KVM: fix KVM_CAP_ARM_SET_DEVICE_ADDR reporting
kvm/ppc/e500: eliminate tlb_refs
kvm/ppc/e500: g2h_tlb1_map: clear old bit before setting new bit
kvm/ppc/e500: h2g_tlb1_rmap: esel 0 is valid
kvm/powerpc/e500mc: fix tlb invalidation on cpu migration
this merge window.
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sfr/next-fixes
Pull powerpc fixes from Stephen Rothwell:
"Three regresions in the PowerPC code. One from v3.7 the others from
this merge window."
* tag 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sfr/next-fixes:
powerpc: add a missing label in resume_kernel
powerpc: Fix audit crash due to save/restore PPR changes
powerpc: fix compiling CONFIG_PPC_TRANSACTIONAL_MEM when CONFIG_ALTIVEC=n
Pull kbuild fix from Michal Marek:
"Fix for a missing dependency when generating scripts/mod/devicetable-offsets.h.
This dependency got introduced in v3.9-rc1."
* 'rc-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild:
kbuild: generate generic headers before recursing into scripts
Pull input fixes from Dmitry Torokhov:
"Two small fixups to the Wacom driver"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input:
Input: wacom - correct reported resolution for Intuos4 Wireless
Input: wacom - fix "can not retrieve extra class descriptor" for 24HDT
Various drivers end up replicating the code to mmap() their memory
buffers into user space, and our core memory remapping function may be
very flexible but it is unnecessarily complicated for the common cases
to use.
Our internal VM uses pfn's ("page frame numbers") which simplifies
things for the VM, and allows us to pass physical addresses around in a
denser and more efficient format than passing a "phys_addr_t" around,
and having to shift it up and down by the page size. But it just means
that drivers end up doing that shifting instead at the interface level.
It also means that drivers end up mucking around with internal VM things
like the vma details (vm_pgoff, vm_start/end) way more than they really
need to.
So this just exports a function to map a certain physical memory range
into user space (using a phys_addr_t based interface that is much more
natural for a driver) and hides all the complexity from the driver.
Some drivers will still end up tweaking the vm_page_prot details for
things like prefetching or cacheability etc, but that's actually
relevant to the driver, rather than caring about what the page offset of
the mapping is into the particular IO memory region.
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Looks like our L_PTE_S2_RDWR definition is slightly wrong,
and is actually write only (see ARM ARM Table B3-9, Stage 2 control
of access permissions). Didn't make a difference for normal pages,
as we OR the flags together, but I'm still wondering how it worked
for Stage-2 mapped devices, such as the GIC.
Brown paper bag time, again.
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <cdall@cs.columbia.edu>
Commit 3401d54696 (KVM: ARM: Introduce KVM_ARM_SET_DEVICE_ADDR
ioctl) added support for the KVM_CAP_ARM_SET_DEVICE_ADDR capability,
but failed to add a break in the relevant case statement, returning
the number of CPUs instead.
Luckilly enough, the CONFIG_NR_CPUS=0 patch hasn't been merged yet
(https://lkml.org/lkml/diff/2012/3/31/131/1), so the bug wasn't
noticed.
Just give it a break!
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <cdall@cs.columbia.edu>
A link-down isn't properly saved in the FEC state, so we wouldn't restart the
FEC after a repeated link-up.
Regression was introduced with commit
d97e7497 "net: fec: restart the FEC when PHY speed changes"
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Tested-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The intention was to test against the constant, not the size of
the constant.
Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: David S. Miller <davem@davemloft.net>
Fixes build with CONFIG_EFI_VARS=m which was broken after the commit
"x86, efivars: firmware bug workarounds should be in platform code".
Signed-off-by: Sergey Vlasov <vsu@altlinux.ru>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
The commit "efi: Distinguish between "remaining space" and actually used
space" added usage of ucs2_*() functions to arch/x86/platform/efi/efi.c,
but the only thing which selected UCS2_STRING was EFI_VARS, which is
technically optional and can be built as a module.
Signed-off-by: Sergey Vlasov <vsu@altlinux.ru>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
The valid mask for both offcore_response_0 and
offcore_response_1 was wrong for SNB/SNB-EP,
IVB/IVB-EP. It was possible to write to
reserved bit and cause a GP fault crashing
the kernel.
This patch fixes the problem by correctly marking the
reserved bits in the valid mask for all the processors
mentioned above.
A distinction between desktop and server parts is introduced
because bits 24-30 are only available on the server parts.
This version of the patch is just a rebase to perf/urgent tree
and should apply to older kernels as well.
Signed-off-by: Stephane Eranian <eranian@google.com>
Cc: peterz@infradead.org
Cc: jolsa@redhat.com
Cc: gregkh@linuxfoundation.org
Cc: security@kernel.org
Cc: ak@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
EFI implementations distinguish between space that is actively used by a
variable and space that merely hasn't been garbage collected yet. Space
that hasn't yet been garbage collected isn't available for use and so isn't
counted in the remaining_space field returned by QueryVariableInfo().
Combined with commit 68d9298 this can cause problems. Some implementations
don't garbage collect until the remaining space is smaller than the maximum
variable size, and as a result check_var_size() will always fail once more
than 50% of the variable store has been used even if most of that space is
marked as available for garbage collection. The user is unable to create
new variables, and deleting variables doesn't increase the remaining space.
The problem that 68d9298 was attempting to avoid was one where certain
platforms fail if the actively used space is greater than 50% of the
available storage space. We should be able to calculate that by simply
summing the size of each available variable and subtracting that from
the total storage space. With luck this will fix the problem described in
https://bugzilla.kernel.org/show_bug.cgi?id=55471 without permitting
damage to occur to the machines 68d9298 was attempting to fix.
Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
EFI variables can be flagged as being accessible only within boot services.
This makes it awkward for us to figure out how much space they use at
runtime. In theory we could figure this out by simply comparing the results
from QueryVariableInfo() to the space used by all of our variables, but
that fails if the platform doesn't garbage collect on every boot. Thankfully,
calling QueryVariableInfo() while still inside boot services gives a more
reliable answer. This patch passes that information from the EFI boot stub
up to the efi platform code.
Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
We want to be able to use the utf16 functions that are currently present
in the EFI variables code in platform-specific code as well. Move them to
the kernel core, and in the process rename them to accurately describe what
they do - they don't handle UTF16, only UCS2.
Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
Dual EMAC slave VLAN id must be got from slave node instead of cpsw node as
VLAN id for each slave will be different.
Reported-by: Mark Jackson <mpfj-list@mimc.co.uk>
Signed-off-by: Mugunthan V N <mugunthanvnm@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
mvneta_tx() was using a static tx queue number causing crashes as
soon as a little bit of traffic was sent via the interface, because
it is normally expected that the same queue should be used as in
dev_queue_xmit().
As suggested by Ben Hutchings, let's use skb_get_queue_mapping() to
get the proper Tx queue number, and use alloc_etherdev_mqs() instead
of alloc_etherdev_mq() to create the queues.
Both my Mirabox and my OpenBlocks AX3 used to crash without this patch
and don't anymore with it. The issue appeared in 3.8 but became more
visible after the fix allowing GSO to be enabled.
Original work was done by Dmitri Epshtein and Thomas Petazzoni. I
just adapted it to take care of Ben's comments.
Signed-off-by: Willy Tarreau <w@1wt.eu>
Cc: Dmitri Epshtein <dima@marvell.com>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Gregory CLEMENT <gregory.clement@free-electrons.com>
Cc: Ben Hutchings <bhutchings@solarflare.com>
Tested-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Fix to return a negative error code from the error handling
case instead of 0, as returned elsewhere in this function.
Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Acked-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Keep a STP port path cost value if it was set by a user.
Don't replace it with the link-speed based path cost
whenever the link goes down and comes back up.
Reported-by: Roopa Prabhu <roopa@cumulusnetworks.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Pull {timer,irq,core} fixes from Thomas Gleixner:
- timer: bug fix for a cpu hotplug race.
- irq: single bugfix for a wrong return value, which prevents the
calling function to invoke the software fallback.
- core: bugfix which plugs two race confitions which can cause hotplug
per cpu threads to end up on the wrong cpu.
* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
hrtimer: Don't reinitialize a cpu_base lock on CPU_UP
* 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
irqchip: gic: fix irq_trigger return
* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
kthread: Prevent unpark race which puts threads on the wrong cpu
The cx25821 driver has support for one audio output channel and two video
output channels.
This is implemented in a very ugly and very evil way through a custom ioctl
that passes the filename of a file containing the video data, which is then
read by the driver itself using vfs.
There are a number of problems with this:
1) it's very ugly and very evil (I can't say that often enough).
2) V4L2 supports video output, so why not use that?
3) it's very buggy, closing the filehandle through which you passed the ioctl
will oops the kernel.
4) it's a nasty security leak since this allows you to load any file in the
system as a video or audio source, so in theory you can output /etc/passwd
to audio or video out and record & decode it on another device.
Because of all these issues we no longer register those output video nodes.
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Trinity discovered that we fail to check all 64 bits of
attr.config passed by user space, resulting to out-of-bounds
access of the perf_swevent_enabled array in
sw_perf_event_destroy().
Introduced in commit b0a873ebb ("perf: Register PMU
implementations").
Signed-off-by: Tommi Rantala <tt.rantala@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: davej@redhat.com
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Link: http://lkml.kernel.org/r/1365882554-30259-1-git-send-email-tt.rantala@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
A label 0 was missed in the patch a9c4e541 (powerpc/kprobe: Complete
kprobe and migrate exception frame). This will cause the kernel
branch to an undetermined address if there really has a conflict when
updating the thread flags.
Signed-off-by: Kevin Hao <haokexin@gmail.com>
Cc: stable@vger.kernel.org
Acked-By: Tiejun Chen <tiejun.chen@windriver.com>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
The current mainline crashes when hitting userspace with the following:
kernel BUG at kernel/auditsc.c:1769!
cpu 0x1: Vector: 700 (Program Check) at [c000000023883a60]
pc: c0000000001047a8: .__audit_syscall_entry+0x38/0x130
lr: c00000000000ed64: .do_syscall_trace_enter+0xc4/0x270
sp: c000000023883ce0
msr: 8000000000029032
current = 0xc000000023800000
paca = 0xc00000000f080380 softe: 0 irq_happened: 0x01
pid = 1629, comm = start_udev
kernel BUG at kernel/auditsc.c:1769!
enter ? for help
[c000000023883d80] c00000000000ed64 .do_syscall_trace_enter+0xc4/0x270
[c000000023883e30] c000000000009b08 syscall_dotrace+0xc/0x38
--- Exception: c00 (System Call) at 0000008010ec50dc
Bisecting found the following patch caused it:
commit 44e9309f1f
Author: Haren Myneni <haren@linux.vnet.ibm.com>
powerpc: Implement PPR save/restore
It was found this patch corrupted r9 when calling
SET_DEFAULT_THREAD_PPR()
Using r10 as a scratch register instead of r9 solved the problem.
Signed-off-by: Alistair Popple <alistair@popple.id.au>
Acked-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Changing uid/gid/projid mappings doesn't change your id within the
namespace; it reconfigures the namespace. Unprivileged programs should
*not* be able to write these files. (We're also checking the privileges
on the wrong task.)
Given the write-once nature of these files and the other security
checks, this is likely impossible to usefully exploit.
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
When we require privilege for setting /proc/<pid>/uid_map or
/proc/<pid>/gid_map no longer allow an unprivileged user to
open the file and pass it to a privileged program to write
to the file.
Instead when privilege is required require both the opener and the
writer to have the necessary capabilities.
I have tested this code and verified that setting /proc/<pid>/uid_map
fails when an unprivileged user opens the file and a privielged user
attempts to set the mapping, that unprivileged users can still map
their own id, and that a privileged users can still setup an arbitrary
mapping.
Reported-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Tomas reported the following build error:
net/built-in.o: In function `ieee80211_unregister_hw':
(.text+0x10f0e1): undefined reference to `unregister_inet6addr_notifier'
net/built-in.o: In function `ieee80211_register_hw':
(.text+0x10f610): undefined reference to `register_inet6addr_notifier'
make: *** [vmlinux] Error 1
when built IPv6 as a module.
So we have to statically link these symbols.
Reported-by: Tomas Melin <tomas.melin@iki.fi>
Cc: Tomas Melin <tomas.melin@iki.fi>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: YOSHIFUJI Hidaki <yoshfuji@linux-ipv6.org>
Signed-off-by: Cong Wang <amwang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Pull x86 fixes from Ingo Molnar:
"Misc fixes"
* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/mm: Flush lazy MMU when DEBUG_PAGEALLOC is set
x86/mm/cpa/selftest: Fix false positive in CPA self test
x86/mm/cpa: Convert noop to functional fix
x86, mm: Patch out arch_flush_lazy_mmu_mode() when running on bare metal
x86, mm, paravirt: Fix vmalloc_fault oops during lazy MMU updates
Pull scheduler fixes from Ingo Molnar:
"Misc fixlets"
* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched/cputime: Fix accounting on multi-threaded processes
sched/debug: Fix sd->*_idx limit range avoiding overflow
sched_clock: Prevent 64bit inatomicity on 32bit systems
sched: Convert BUG_ON()s in try_to_wake_up_local() to WARN_ON_ONCE()s
Pull drm fixes from Dave Airlie:
"One fix for a hotplug locking regressions, and one fix for an oops if
you unplug the monitor at an inopportune moment on the udl device."
* 'drm-fixes' of git://people.freedesktop.org/~airlied/linux:
drm/fb-helper: Fix locking in drm_fb_helper_hotplug_event
udl: handle EDID failure properly.
Pull m68knommu fix from Greg Ungerer:
"This contains only a single compilation fix for ColdFire m68k targets
that use local non-GPIOLIB support."
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/gerg/m68knommu:
m68k: define a local gpio_request_one() function
Pull watchdog fix from Wim Van Sebroeck:
"It will fix compile errors for the at91rm9200_wdt driver"
* git://www.linux-watchdog.org/linux-watchdog:
watchdog: Revert the AT91RM9200_WATCHDOG dependency
Pull one more btrfs fix from Chris Mason:
"This has a recent fix from Josef for our tree log replay code. It
fixes problems where the inode counter for the number of bytes in the
file wasn't getting updated properly during fsync replay.
The commit did get rebased this morning, but it was only to clean up
the subject line. The code hasn't changed."
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs:
Btrfs: make sure nbytes are right after log replay
doing: echo 1234 | tee -a /sys/kernel/debug/tracing/set_ftrace_pid
Luckily, this can only be done by root, but still is a nasty bug.
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Merge tag 'trace-fixes-v3.9-rc-v3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
Pull ftrace fixes from Steven Rostedt:
"Namhyung Kim found and fixed a bug that can crash the kernel by simply
doing: echo 1234 | tee -a /sys/kernel/debug/tracing/set_ftrace_pid
Luckily, this can only be done by root, but still is a nasty bug."
* tag 'trace-fixes-v3.9-rc-v3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
ftrace: Move ftrace_filter_lseek out of CONFIG_DYNAMIC_FTRACE section
tracing: Fix possible NULL pointer dereferences
Nothing is using it yet, but this will allow us to delay the open-time
checks to use time, without breaking the normal UNIX permission
semantics where permissions are determined by the opener (and the file
descriptor can then be passed to a different process, or the process can
drop capabilities).
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Compiling the at91rm9200_wdt.c driver without at91rm9200
support was leading to several errors:
drivers/built-in.o: In function `at91_wdt_close':
at91_adc.c:(.text+0xc9fe4): undefined reference to `at91_st_base'
drivers/built-in.o: In function `at91_wdt_write':
at91_adc.c:(.text+0xca004): undefined reference to `at91_st_base'
drivers/built-in.o: In function `at91wdt_shutdown':
at91_adc.c:(.text+0xca01c): undefined reference to `at91_st_base'
drivers/built-in.o: In function `at91wdt_suspend':
at91_adc.c:(.text+0xca038): undefined reference to `at91_st_base'
drivers/built-in.o: In function `at91_wdt_open':
at91_adc.c:(.text+0xca0cc): undefined reference to `at91_st_base'
drivers/built-in.o:at91_adc.c:(.text+0xca2c8): more undefined references to
`at91_st_base' follow
So, reverting the modification of the "depends" Kconfig line
introduced by patch a6a1bcd37 (watchdog: at91rm9200: add DT support)
seems to be the good solution.
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Acked-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
Revert commit 62a3ddef61 ("vfs: fix spinning prevention in prune_icache_sb").
This commit doesn't look right: since we are looking at the tail of the
list (sb->s_inode_lru.prev) if we want to skip an inode, we should put
it back at the head of the list instead of the tail, otherwise we will
keep spinning on it.
Discovered when investigating why prune_icache_sb came top in perf
reports of a swapping load.
Signed-off-by: Suleiman Souhlal <suleiman@google.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: stable@vger.kernel.org # v3.2+
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Anatol Pomozov identified a race condition that hits module unloading
and re-loading. To quote Anatol:
"This is a race codition that exists between kset_find_obj() and
kobject_put(). kset_find_obj() might return kobject that has refcount
equal to 0 if this kobject is freeing by kobject_put() in other
thread.
Here is timeline for the crash in case if kset_find_obj() searches for
an object tht nobody holds and other thread is doing kobject_put() on
the same kobject:
THREAD A (calls kset_find_obj()) THREAD B (calls kobject_put())
splin_lock()
atomic_dec_return(kobj->kref), counter gets zero here
... starts kobject cleanup ....
spin_lock() // WAIT thread A in kobj_kset_leave()
iterate over kset->list
atomic_inc(kobj->kref) (counter becomes 1)
spin_unlock()
spin_lock() // taken
// it does not know that thread A increased counter so it
remove obj from list
spin_unlock()
vfree(module) // frees module object with containing kobj
// kobj points to freed memory area!!
kobject_put(kobj) // OOPS!!!!
The race above happens because module.c tries to use kset_find_obj()
when somebody unloads module. The module.c code was introduced in
commit 6494a93d55fa"
Anatol supplied a patch specific for module.c that worked around the
problem by simply not using kset_find_obj() at all, but rather than make
a local band-aid, this just fixes kset_find_obj() to be thread-safe
using the proper model of refusing the get a new reference if the
refcount has already dropped to zero.
See examples of this proper refcount handling not only in the kref
documentation, but in various other equivalent uses of this pattern by
grepping for atomic_inc_not_zero().
[ Side note: the module race does indicate that module loading and
unloading is not properly serialized wrt sysfs information using the
module mutex. That may require further thought, but this is the
correct fix at the kobject layer regardless. ]
Reported-analyzed-and-tested-by: Anatol Pomozov <anatol.pomozov@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
