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Jann Horn 6994eefb00 ptrace: Fix ->ptracer_cred handling for PTRACE_TRACEME 
Fix two issues:

When called for PTRACE_TRACEME, ptrace_link() would obtain an RCU
reference to the parent's objective credentials, then give that pointer
to get_cred().  However, the object lifetime rules for things like
struct cred do not permit unconditionally turning an RCU reference into
a stable reference.

PTRACE_TRACEME records the parent's credentials as if the parent was
acting as the subject, but that's not the case.  If a malicious
unprivileged child uses PTRACE_TRACEME and the parent is privileged, and
at a later point, the parent process becomes attacker-controlled
(because it drops privileges and calls execve()), the attacker ends up
with control over two processes with a privileged ptrace relationship,
which can be abused to ptrace a suid binary and obtain root privileges.

Fix both of these by always recording the credentials of the process
that is requesting the creation of the ptrace relationship:
current_cred() can't change under us, and current is the proper subject
for access control.

This change is theoretically userspace-visible, but I am not aware of
any code that it will actually break.

Fixes: 64b875f7ac ("ptrace: Capture the ptracer's creds not PT_PTRACE_CAP")
Signed-off-by: Jann Horn <jannh@google.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-07-05 02:00:41 +09:00
..
bpf SPDX update for 5.2-rc6 2019-06-21 09:58:42 -07:00
cgroup treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 451 2019-06-19 17:09:08 +02:00
configs
debug treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
dma treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 333 2019-06-05 17:37:06 +02:00
events perf/x86: Disable extended registers for non-supported PMUs 2019-06-24 19:19:23 +02:00
gcov treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
irq treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
livepatch This includes the following fixes: 2019-06-15 07:24:11 -10:00
locking treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 436 2019-06-05 17:37:17 +02:00
power PCI: PM: Avoid skipping bus-level PM on platforms without ACPI 2019-06-26 23:51:56 +02:00
printk treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 13 2019-05-21 11:28:45 +02:00
rcu treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
sched treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
time timekeeping: Repair ktime_get_coarse*() granularity 2019-06-14 11:51:44 +02:00
trace This includes three fixes: 2019-07-04 10:26:17 +09:00
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acct.c
async.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 441 2019-06-05 17:37:17 +02:00
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context_tracking.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
cpu.c cpu/hotplug: Fix out-of-bounds read when setting fail state 2019-06-27 09:34:04 +02:00
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cred.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2019-06-11 15:44:45 -10:00
delayacct.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 25 2019-05-21 11:52:39 +02:00
dma.c
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exit.c cgroup: Call cgroup_release() before __exit_signal() 2019-05-31 10:38:57 -07:00
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fork.c fork: return proper negative error code 2019-07-01 16:43:30 +02:00
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gen_kheaders.sh kheaders: Do not regenerate archive if config is not changed 2019-05-24 20:16:01 +02:00
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Makefile kheaders: Move from proc to sysfs 2019-05-24 20:16:01 +02:00
memremap.c mm/devm_memremap_pages: fix final page put race 2019-06-13 17:34:56 -10:00
module-internal.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 36 2019-05-24 17:27:11 +02:00
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pid.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
pid_namespace.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
profile.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
ptrace.c ptrace: Fix ->ptracer_cred handling for PTRACE_TRACEME 2019-07-05 02:00:41 +09:00
range.c
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signal.c signal: remove the wrong signal_pending() check in restore_user_sigmask() 2019-06-29 16:43:45 +08:00
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smpboot.h
softirq.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 430 2019-06-05 17:37:16 +02:00
stackleak.c
stacktrace.c Merge branch 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-06-02 11:04:42 -07:00
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sys.c prctl_set_mm: downgrade mmap_sem to read lock 2019-06-01 15:51:31 -07:00
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sysctl.c sysctl: define proc_do_static_key() 2019-06-14 20:18:27 -07:00
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