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Luis R. Rodriguez 4f2fec00af sysctl: simplify unsigned int support 
Commit e7d316a02f ("sysctl: handle error writing UINT_MAX to u32
fields") added proc_douintvec() to start help adding support for
unsigned int, this however was only half the work needed.  Two fixes
have come in since then for the following issues:

  o Printing the values shows a negative value, this happens since
    do_proc_dointvec() and this uses proc_put_long()

This was fixed by commit 5380e5644a ("sysctl: don't print negative
flag for proc_douintvec").

  o We can easily wrap around the int values: UINT_MAX is 4294967295, if
    we echo in 4294967295 + 1 we end up with 0, using 4294967295 + 2 we
    end up with 1.
  o We echo negative values in and they are accepted

This was fixed by commit 425fffd886 ("sysctl: report EINVAL if value
is larger than UINT_MAX for proc_douintvec").

It still also failed to be added to sysctl_check_table()...  instead of
adding it with the current implementation just provide a proper and
simplified unsigned int support without any array unsigned int support
with no negative support at all.

Historically sysctl proc helpers have supported arrays, due to the
complexity this adds though we've taken a step back to evaluate array
users to determine if its worth upkeeping for unsigned int.  An
evaluation using Coccinelle has been done to perform a grammatical
search to ask ourselves:

  o How many sysctl proc_dointvec() (int) users exist which likely
    should be moved over to proc_douintvec() (unsigned int) ?
	Answer: about 8
	- Of these how many are array users ?
		Answer: Probably only 1
  o How many sysctl array users exist ?
	Answer: about 12

This last question gives us an idea just how popular arrays: they are not.
Array support should probably just be kept for strings.

The identified uint ports are:

  drivers/infiniband/core/ucma.c - max_backlog
  drivers/infiniband/core/iwcm.c - default_backlog
  net/core/sysctl_net_core.c - rps_sock_flow_sysctl()
  net/netfilter/nf_conntrack_timestamp.c - nf_conntrack_timestamp -- bool
  net/netfilter/nf_conntrack_acct.c nf_conntrack_acct -- bool
  net/netfilter/nf_conntrack_ecache.c - nf_conntrack_events -- bool
  net/netfilter/nf_conntrack_helper.c - nf_conntrack_helper -- bool
  net/phonet/sysctl.c proc_local_port_range()

The only possible array users is proc_local_port_range() but it does not
seem worth it to add array support just for this given the range support
works just as well.  Unsigned int support should be desirable more for
when you *need* more than INT_MAX or using int min/max support then does
not suffice for your ranges.

If you forget and by mistake happen to register an unsigned int proc
entry with an array, the driver will fail and you will get something as
follows:

sysctl table check failed: debug/test_sysctl//uint_0002 array now allowed
CPU: 2 PID: 1342 Comm: modprobe Tainted: G        W   E <etc>
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS <etc>
Call Trace:
 dump_stack+0x63/0x81
 __register_sysctl_table+0x350/0x650
 ? kmem_cache_alloc_trace+0x107/0x240
 __register_sysctl_paths+0x1b3/0x1e0
 ? 0xffffffffc005f000
 register_sysctl_table+0x1f/0x30
 test_sysctl_init+0x10/0x1000 [test_sysctl]
 do_one_initcall+0x52/0x1a0
 ? kmem_cache_alloc_trace+0x107/0x240
 do_init_module+0x5f/0x200
 load_module+0x1867/0x1bd0
 ? __symbol_put+0x60/0x60
 SYSC_finit_module+0xdf/0x110
 SyS_finit_module+0xe/0x10
 entry_SYSCALL_64_fastpath+0x1e/0xad
RIP: 0033:0x7f042b22d119
<etc>

Fixes: e7d316a02f ("sysctl: handle error writing UINT_MAX to u32 fields")
Link: http://lkml.kernel.org/r/20170519033554.18592-5-mcgrof@kernel.org
Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
Suggested-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>
Cc: Liping Zhang <zlpnobody@gmail.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>
Cc: Kees Cook <keescook@chromium.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 		2017-07-12 16:26:00 -07:00
Documentation kexec/kdump: minor Documentation updates for arm64 and Image 2017-07-12 16:26:00 -07:00
arch powerpc/fadump: use the correct VMCOREINFO_NOTE_SIZE for phdr 2017-07-12 16:25:59 -07:00
block Merge branch 'for-linus' of git://git.kernel.dk/linux-block 2017-07-11 15:36:52 -07:00
certs scripts/spelling.txt: add "intialise(d)" pattern and fix typo instances 2017-05-08 17:15:13 -07:00
crypto dmaengine updates for 4.13-rc1 2017-07-08 12:36:50 -07:00
drivers Merge branch 'i2c/for-4.13' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux 2017-07-12 10:04:56 -07:00
firmware firmware/Makefile: force recompilation if makefile changes 2017-05-08 17:15:10 -07:00
fs sysctl: simplify unsigned int support 2017-07-12 16:26:00 -07:00
include kdump: protect vmcoreinfo data under the crash memory 2017-07-12 16:26:00 -07:00
init mm: allow slab_nomerge to be set at build time 2017-07-06 16:24:31 -07:00
ipc mqueue: fix a use-after-free in sys_mq_notify() 2017-07-09 14:37:19 -07:00
kernel sysctl: simplify unsigned int support 2017-07-12 16:26:00 -07:00
lib lib/bsearch.c: micro-optimize pivot position calculation 2017-07-10 16:32:35 -07:00
mm mm/memory.c: mark create_huge_pmd() inline to prevent build failure 2017-07-12 16:25:59 -07:00
net The main item here is support for v12.y.z ("Luminous") clusters: 2017-07-11 12:12:28 -07:00
samples bpf: fix return in load_bpf_file 2017-07-05 09:05:28 +01:00
scripts checkpatch: improve multi-line alignment test 2017-07-10 16:32:35 -07:00
security Merge branch 'work.memdup_user' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-07-05 16:05:24 -07:00
sound main drm pull for v4.13 2017-07-09 18:48:37 -07:00
tools Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-07-09 10:49:47 -07:00
usr ramfs: clarify help text that compression applies to ramfs as well as legacy ramdisk. 2017-07-06 16:24:30 -07:00
virt PPC: 2017-07-06 18:38:31 -07:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore
…
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore kbuild: Add support to generate LLVM assembly files 2017-04-25 08:13:52 +09:00
.mailmap power supply and reset changes for the v4.12 series (part 2) 2017-05-12 12:02:21 -07:00
COPYING
…
CREDITS avr32: remove support for AVR32 architecture 2017-05-01 09:27:15 +02:00
Kbuild kbuild: Consolidate header generation from ASM offset information 2017-04-13 05:43:37 +09:00
Kconfig
…
MAINTAINERS Merge branch 'i2c/for-4.13' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux 2017-07-12 10:04:56 -07:00
Makefile Kbuild thin archives updates for v4.13 2017-07-07 15:11:12 -07:00
README README: add a new README file, pointing to the Documentation/ 2016-10-24 08:12:35 -02:00

README 

Linux kernel
============

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.