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Michael Ellerman c7def7fbde powerpc/64/tm: Don't let userspace set regs->trap via sigreturn 
In restore_tm_sigcontexts() we take the trap value directly from the
user sigcontext with no checking:

	err |= __get_user(regs->trap, &sc->gp_regs[PT_TRAP]);

This means we can be in the kernel with an arbitrary regs->trap value.

Although that's not immediately problematic, there is a risk we could
trigger one of the uses of CHECK_FULL_REGS():

	#define CHECK_FULL_REGS(regs)	BUG_ON(regs->trap & 1)

It can also cause us to unnecessarily save non-volatile GPRs again in
save_nvgprs(), which shouldn't be problematic but is still wrong.

It's also possible it could trick the syscall restart machinery, which
relies on regs->trap not being == 0xc00 (see 9a81c16b52 ("powerpc:
fix double syscall restarts")), though I haven't been able to make
that happen.

Finally it doesn't match the behaviour of the non-TM case, in
restore_sigcontext() which zeroes regs->trap.

So change restore_tm_sigcontexts() to zero regs->trap.

This was discovered while testing Nick's upcoming rewrite of the
syscall entry path. In that series the call to save_nvgprs() prior to
signal handling (do_notify_resume()) is removed, which leaves the
low-bit of regs->trap uncleared which can then trigger the FULL_REGS()
WARNs in setup_tm_sigcontexts().

Fixes: 2b0a576d15 ("powerpc: Add new transactional memory state to the signal context")
Cc: stable@vger.kernel.org # v3.9+
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200401023836.3286664-1-mpe@ellerman.id.au
 		2020-04-01 13:42:00 +11:00
Documentation powerpc/fadump: sysfs for fadump memory reservation 2020-02-19 22:46:07 +11:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
arch powerpc/64/tm: Don't let userspace set regs->trap via sigreturn 2020-04-01 13:42:00 +11:00
block block-5.6-2020-02-05 2020-02-06 06:15:23 +00:00
certs certs: Add wrapper function to check blacklisted binary hash 2019-11-12 12:25:50 +11:00
crypto s390 updates for 5.6-rc2 2020-02-15 13:10:38 -08:00
drivers powerpc/eeh: Make early EEH init pseries specific 2020-03-25 12:09:39 +11:00
fs sysfs: Wrap __compat_only_sysfs_link_entry_to_kobj function to change the symlink name 2020-02-19 21:07:09 +11:00
include sysfs: Wrap __compat_only_sysfs_link_entry_to_kobj function to change the symlink name 2020-02-19 21:07:09 +11:00
init Various fixes: 2020-02-11 16:39:18 -08:00
ipc proc: convert everything to "struct proc_ops" 2020-02-04 03:05:26 +00:00
kernel Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2020-02-15 12:51:22 -08:00
lib Various fixes: 2020-02-11 16:39:18 -08:00
mm Merge branch 'merge.nfs-fs_parse.1' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-02-08 13:26:41 -08:00
net NFS Client Bugfixes for Linux 5.6-rc2 2020-02-14 14:46:11 -08:00
samples Kbuild updates for v5.6 (2nd) 2020-02-09 16:05:50 -08:00
scripts kbuild: fix mismatch between .version and include/generated/compile.h 2020-02-11 05:18:40 +09:00
security selinux/stable-5.6 PR 20200210 2020-02-10 16:51:35 -08:00
sound ALSA: pcm: Fix double hw_free calls 2020-02-13 16:30:22 +01:00
tools selftests/powerpc: Turn off timeout setting for benchmarks, dscr, signal, tm 2020-03-25 12:09:30 +11:00
usr Kbuild updates for v5.6 (2nd) 2020-02-09 16:05:50 -08:00
virt KVM: Disable preemption in kvm_get_running_vcpu() 2020-02-12 12:19:35 +01:00
.clang-format clang-format: Update with the latest for_each macro list 2019-08-31 10:00:51 +02:00
.cocciconfig
…
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore modpost: dump missing namespaces into a single modules.nsdeps file 2019-11-11 20:10:01 +09:00
.mailmap A handful of small documentation fixes that wandered in. 2020-02-07 13:03:10 -08:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS open: introduce openat2(2) syscall 2020-01-18 09:19:18 -05:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS powerpc: Switch 8xx MAINTAINERS entry to Christophe 2020-03-27 01:12:56 +11:00
Makefile Linux 5.6-rc2 2020-02-16 13:16:59 -08:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

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

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

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.