linux-stable.git/arch/um, branch v3.2.73 Linux kernel stable tree vm: add VM_FAULT_SIGSEGV handling support 2015-02-20T00:49:40+00:00 Linus Torvalds torvalds@linux-foundation.org 2015-01-29T18:51:32+00:00 219a047eb9a3cde86b5a341f9f8d4f6cf7e8cd56 commit 33692f27597fcab536d7cbbcc8f52905133e4aa7 upstream. The core VM already knows about VM_FAULT_SIGBUS, but cannot return a "you should SIGSEGV" error, because the SIGSEGV case was generally handled by the caller - usually the architecture fault handler. That results in lots of duplication - all the architecture fault handlers end up doing very similar "look up vma, check permissions, do retries etc" - but it generally works. However, there are cases where the VM actually wants to SIGSEGV, and applications _expect_ SIGSEGV. In particular, when accessing the stack guard page, libsigsegv expects a SIGSEGV. And it usually got one, because the stack growth is handled by that duplicated architecture fault handler. However, when the generic VM layer started propagating the error return from the stack expansion in commit fee7e49d4514 ("mm: propagate error from stack expansion even for guard page"), that now exposed the existing VM_FAULT_SIGBUS result to user space. And user space really expected SIGSEGV, not SIGBUS. To fix that case, we need to add a VM_FAULT_SIGSEGV, and teach all those duplicate architecture fault handlers about it. They all already have the code to handle SIGSEGV, so it's about just tying that new return value to the existing code, but it's all a bit annoying. This is the mindless minimal patch to do this. A more extensive patch would be to try to gather up the mostly shared fault handling logic into one generic helper routine, and long-term we really should do that cleanup. Just from this patch, you can generally see that most architectures just copied (directly or indirectly) the old x86 way of doing things, but in the meantime that original x86 model has been improved to hold the VM semaphore for shorter times etc and to handle VM_FAULT_RETRY and other "newer" things, so it would be a good idea to bring all those improvements to the generic case and teach other architectures about them too. Reported-and-tested-by: Takashi Iwai <tiwai@suse.de> Tested-by: Jan Engelhardt <jengelh@inai.de> Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com> # "s390 still compiles and boots" Cc: linux-arch@vger.kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> [bwh: Backported to 3.2: - Adjust filenames, context - Drop arc, metag, nios2 and lustre changes - For sh, patch both 32-bit and 64-bit implementations to use goto bad_area - For s390, pass int_code and trans_exc_code as arguments to do_no_context() and do_sigsegv()] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit 33692f27597fcab536d7cbbcc8f52905133e4aa7 upstream.

The core VM already knows about VM_FAULT_SIGBUS, but cannot return a
"you should SIGSEGV" error, because the SIGSEGV case was generally
handled by the caller - usually the architecture fault handler.

That results in lots of duplication - all the architecture fault
handlers end up doing very similar "look up vma, check permissions, do
retries etc" - but it generally works.  However, there are cases where
the VM actually wants to SIGSEGV, and applications _expect_ SIGSEGV.

In particular, when accessing the stack guard page, libsigsegv expects a
SIGSEGV.  And it usually got one, because the stack growth is handled by
that duplicated architecture fault handler.

However, when the generic VM layer started propagating the error return
from the stack expansion in commit fee7e49d4514 ("mm: propagate error
from stack expansion even for guard page"), that now exposed the
existing VM_FAULT_SIGBUS result to user space.  And user space really
expected SIGSEGV, not SIGBUS.

To fix that case, we need to add a VM_FAULT_SIGSEGV, and teach all those
duplicate architecture fault handlers about it.  They all already have
the code to handle SIGSEGV, so it's about just tying that new return
value to the existing code, but it's all a bit annoying.

This is the mindless minimal patch to do this.  A more extensive patch
would be to try to gather up the mostly shared fault handling logic into
one generic helper routine, and long-term we really should do that
cleanup.

Just from this patch, you can generally see that most architectures just
copied (directly or indirectly) the old x86 way of doing things, but in
the meantime that original x86 model has been improved to hold the VM
semaphore for shorter times etc and to handle VM_FAULT_RETRY and other
"newer" things, so it would be a good idea to bring all those
improvements to the generic case and teach other architectures about
them too.

Reported-and-tested-by: Takashi Iwai <tiwai@suse.de>
Tested-by: Jan Engelhardt <jengelh@inai.de>
Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com> # "s390 still compiles and boots"
Cc: linux-arch@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[bwh: Backported to 3.2:
 - Adjust filenames, context
 - Drop arc, metag, nios2 and lustre changes
 - For sh, patch both 32-bit and 64-bit implementations to use goto bad_area
 - For s390, pass int_code and trans_exc_code as arguments to do_no_context()
   and do_sigsegv()]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
um: add missing declaration of 'getrlimit()' and friends 2014-01-03T04:33:31+00:00 Sergei Trofimovich slyfox@gentoo.org 2012-12-29T22:37:30+00:00 dc55b2a5a8f2abd303198c8169c52550a010391d commit fdfa4c952844fce881df8c76de9c7180cbe913ab upstream. arch/um/os-Linux/start_up.c: In function 'check_coredump_limit': arch/um/os-Linux/start_up.c:338:16: error: storage size of 'lim' isn't known arch/um/os-Linux/start_up.c:339:2: error: implicit declaration of function 'getrlimit' [-Werror=implicit-function-declaration] Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org> CC: Jeff Dike <jdike@addtoit.com> CC: Richard Weinberger <richard@nod.at> CC: Al Viro <viro@zeniv.linux.org.uk> CC: user-mode-linux-devel@lists.sourceforge.net CC: user-mode-linux-user@lists.sourceforge.net CC: linux-kernel@vger.kernel.org Signed-off-by: Richard Weinberger <richard@nod.at> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit fdfa4c952844fce881df8c76de9c7180cbe913ab upstream.

arch/um/os-Linux/start_up.c: In function 'check_coredump_limit':
arch/um/os-Linux/start_up.c:338:16: error: storage size of 'lim' isn't known
arch/um/os-Linux/start_up.c:339:2: error: implicit declaration of function 'getrlimit' [-Werror=implicit-function-declaration]

Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
CC: Jeff Dike <jdike@addtoit.com>
CC: Richard Weinberger <richard@nod.at>
CC: Al Viro <viro@zeniv.linux.org.uk>
CC: user-mode-linux-devel@lists.sourceforge.net
CC: user-mode-linux-user@lists.sourceforge.net
CC: linux-kernel@vger.kernel.org
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
uml: check length in exitcode_proc_write() 2013-11-28T14:02:06+00:00 Dan Carpenter dan.carpenter@oracle.com 2013-10-29T19:06:04+00:00 02c54b6cf2b7bd1089bef485d7a81bdf0c5999d8 commit 201f99f170df14ba52ea4c52847779042b7a623b upstream. We don't cap the size of buffer from the user so we could write past the end of the array here. Only root can write to this file. Reported-by: Nico Golde <nico@ngolde.de> Reported-by: Fabian Yamaguchi <fabs@goesec.de> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit 201f99f170df14ba52ea4c52847779042b7a623b upstream.

We don't cap the size of buffer from the user so we could write past the
end of the array here.  Only root can write to this file.

Reported-by: Nico Golde <nico@ngolde.de>
Reported-by: Fabian Yamaguchi <fabs@goesec.de>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
um: Serve io_remap_pfn_range() 2013-05-30T13:35:15+00:00 Richard Weinberger richard@nod.at 2012-02-07T00:22:47+00:00 8cd656dbac3dca07869aab089b600133786cee34 commit 4d94d6d030adfdea4837694d293ec6918d133ab2 upstream. At some places io_remap_pfn_range() is needed. UML has to serve it like all other archs do. Signed-off-by: Richard Weinberger <richard@nod.at> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit 4d94d6d030adfdea4837694d293ec6918d133ab2 upstream.

At some places io_remap_pfn_range() is needed.
UML has to serve it like all other archs do.

Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
um: Fix __swp_type() 2012-05-30T23:43:47+00:00 Richard Weinberger richard@nod.at 2012-04-14T15:46:01+00:00 ff741084d380bd234a4d0ffba0c19e8047a14658 commit 2b76ebaa728f8a3967c52aa189261c72fe56a6f1 upstream. The current __swp_type() function uses a too small bitshift. Using more than one swap files causes bad pages because the type bits clash with other page flags. Analyzed-by: Hugh Dickins <hughd@google.com> Signed-off-by: Richard Weinberger <richard@nod.at> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit 2b76ebaa728f8a3967c52aa189261c72fe56a6f1 upstream.

The current __swp_type() function uses a too small bitshift.
Using more than one swap files causes bad pages because
the type bits clash with other page flags.

Analyzed-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
um: Implement a custom pte_same() function 2012-05-30T23:43:46+00:00 Richard Weinberger richard@nod.at 2012-04-14T15:29:30+00:00 e22b65022898e212f80ca989e613179e318b8a79 commit f15b9000eb1d09bbaa4b0a6b2089d7e1f64e84b3 upstream. UML uses the _PAGE_NEWPAGE flag to mark pages which are not jet installed on the host side using mmap(). pte_same() has to ignore this flag, otherwise unuse_pte_range() is unable to unuse the page because two identical page tables entries with different _PAGE_NEWPAGE flags would not match and swapoff() would never return. Analyzed-by: Hugh Dickins <hughd@google.com> Signed-off-by: Richard Weinberger <richard@nod.at> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit f15b9000eb1d09bbaa4b0a6b2089d7e1f64e84b3 upstream.

UML uses the _PAGE_NEWPAGE flag to mark pages which are not jet
installed on the host side using mmap().
pte_same() has to ignore this flag, otherwise unuse_pte_range()
is unable to unuse the page because two identical
page tables entries with different _PAGE_NEWPAGE flags would not
match and swapoff() would never return.

Analyzed-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Merge branch 'for-linus' of git://github.com/richardweinberger/linux 2011-11-02T16:45:39+00:00 Linus Torvalds torvalds@linux-foundation.org 2011-11-02T16:45:39+00:00 de0a5345a55b8dd5a4695181275df0e691176830 * 'for-linus' of git://github.com/richardweinberger/linux: (90 commits) um: fix ubd cow size um: Fix kmalloc argument order in um/vdso/vma.c um: switch to use of drivers/Kconfig UserModeLinux-HOWTO.txt: fix a typo UserModeLinux-HOWTO.txt: remove ^H characters um: we need sys/user.h only on i386 um: merge delay_{32,64}.c um: distribute exports to where exported stuff is defined um: kill system-um.h um: generic ftrace.h will do... um: segment.h is x86-only and needed only there um: asm/pda.h is not needed anymore um: hw_irq.h can go generic as well um: switch to generic-y um: clean Kconfig up a bit um: a couple of missing dependencies... um: kill useless argument of free_chan() and free_one_chan() um: unify ptrace_user.h um: unify KSTK_... um: fix gcov build breakage ... 
* 'for-linus' of git://github.com/richardweinberger/linux: (90 commits)
  um: fix ubd cow size
  um: Fix kmalloc argument order in um/vdso/vma.c
  um: switch to use of drivers/Kconfig
  UserModeLinux-HOWTO.txt: fix a typo
  UserModeLinux-HOWTO.txt: remove ^H characters
  um: we need sys/user.h only on i386
  um: merge delay_{32,64}.c
  um: distribute exports to where exported stuff is defined
  um: kill system-um.h
  um: generic ftrace.h will do...
  um: segment.h is x86-only and needed only there
  um: asm/pda.h is not needed anymore
  um: hw_irq.h can go generic as well
  um: switch to generic-y
  um: clean Kconfig up a bit
  um: a couple of missing dependencies...
  um: kill useless argument of free_chan() and free_one_chan()
  um: unify ptrace_user.h
  um: unify KSTK_...
  um: fix gcov build breakage
  ...
um: fix ubd cow size 2011-11-02T13:15:42+00:00 Richard Weinberger richard@nod.at 2011-11-02T12:17:27+00:00 8535639810e578960233ad39def3ac2157b0c3ec ubd_file_size() cannot use ubd_dev->cow.file because at this time ubd_dev->cow.file is not initialized. Therefore, ubd_file_size() will always report a wrong disk size when COW files are used. Reading from /dev/ubd* would crash the kernel. We have to read the correct disk size from the COW file's backing file. Signed-off-by: Richard Weinberger <richard@nod.at> CC: stable@kernel.org 
ubd_file_size() cannot use ubd_dev->cow.file because at this time
ubd_dev->cow.file is not initialized.
Therefore, ubd_file_size() will always report a wrong disk size when
COW files are used.
Reading from /dev/ubd* would crash the kernel.

We have to read the correct disk size from the COW file's backing
file.

Signed-off-by: Richard Weinberger <richard@nod.at>
CC: stable@kernel.org
um: switch to use of drivers/Kconfig 2011-11-02T13:15:41+00:00 Al Viro viro@ftp.linux.org.uk 2011-08-18T19:11:59+00:00 3369465ed1a6a9aa9b885a6d7d8e074ecbd782da Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Richard Weinberger <richard@nod.at> 
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Richard Weinberger <richard@nod.at>
um: distribute exports to where exported stuff is defined 2011-11-02T13:15:36+00:00 Al Viro viro@ftp.linux.org.uk 2011-08-18T19:14:10+00:00 73395a0002aa9573ffc8d989587b79663847f705 ksyms.c is down to the stuff defined in various USER_OBJS Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Richard Weinberger <richard@nod.at> 
ksyms.c is down to the stuff defined in various USER_OBJS

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Richard Weinberger <richard@nod.at>