Similar to the way we handle LIBC_DEBUG_MALLOC_OPTIONS
(bug 68003719), filter LIBC_HOOKS_ENABLE when we cross a
security boundary. This prevents modifying the allocation
behavior of a privileged program.
Introduced in
db478a6274%5E%21/#F0
(bug 30561479)
Test: compiles and boots
Change-Id: I59a7c224734b0991fd62efb45ab599dab8570723
For security reasons, when a binary is executed which causes a security
transition (eg, a setuid binary, setgid binary, filesystem capabilities,
or SELinux domain transition), the AT_SECURE flag is set. This causes
certain blacklisted environment variables to be stripped before the
process is executed. The list of blacklisted environment variables is
stored in UNSAFE_VARIABLE_NAMES. Generally speaking, most environment
variables used internally by libc show up in this list.
Commit 02586a2a34 ("linker: the
global group is added to all built-in namespaces", Aug 2017) added
support for the environment variable LD_CONFIG_FILE. This debug build
only feature allows the caller to specify the path to the loader
configuration file. Like other linker environment variables, setting
this variable allows the calling process to control executed code of the
called process, which has security implications (on debuggable builds
only).
Add LD_CONFIG_FILE to UNSAFE_VARIABLE_NAMES. This has the effect of
stripping, on all build types, the LD_CONFIG_FILE environment variable.
This has three advantages:
1) Prevents security bugs should LD_CONFIG_FILE ever be inadvertantly
exposed on a production build.
2) Makes the behavior of userdebug and user builds more similar, helping
prevent build-type dependent bugs where someone may come to rely on this
debug-only feature.
3) Protect droidfood users against malicious applications which can
trigger a security transition, eg, the execution of crash_dump or the
renderscript compiler.
Alternative considered but rejected:
If we treated LD_CONFIG_FILE like LD_PRELOAD, we could expose this on
all build types, and remove the build-type dependent behavior. But this
is contrary to enh's Aug 02 2017 guidance at
https://android-review.googlesource.com/c/platform/bionic/+/449956
i'm still uncomfortable about LD_CONFIG_FILE because i'd like
to be reducing the number of environment variables that affect
the linker in P rather than increasing them.
Test: atest CtsBionicTestCases
Test: atest linker-unit-tests
Change-Id: I82d286546ee079b5cde04428dc89941c253c2d20
File descriptor confusion can result if a process is exec()d and
STDIN/STDOUT/STDERR do not exist. In those situations, the first,
second, and third files opened by the exec()d application will have FD
0, 1, and 2 respectively. Code which reads / writes to these STD* file
descriptors may end up reading / writing to unintended files.
To prevent this, guarantee that FDs 0, 1, and 2 always exist. Bionic
only currently guarantees this for AT_SECURE programs (eg, a setuid
binary, setgid binary, filesystem capabilities, or SELinux domain
transition).
Extending this to all exec()s adds robustness against this class of
bugs. Additionally, it allows a caller to do:
close(STDIN_FILENO);
close(STDOUT_FILENO);
close(STDERR_FILENO);
and know that the exec()d process will reopen these file descriptors on
its own. This has the potential to simplify other parts of Android, eg
https://android-review.googlesource.com/c/platform/system/apex/+/915694
Steps to reproduce:
sleep 100 <&- >&- 2>&- & BGPID=$! && ls -la /proc/$BGPID/fd && kill $BGPID
Expected:
$ sleep 100 <&- >&- 2>&- & BGPID=$! && ls -la /proc/$BGPID/fd && kill $BGPID
[1] 3154
total 0
dr-x------ 2 shell shell 0 1970-04-17 12:15 .
dr-xr-xr-x 9 shell shell 0 1970-04-17 12:15 ..
lrwx------ 1 shell shell 64 1970-04-17 12:15 0 -> /dev/null
lrwx------ 1 shell shell 64 1970-04-17 12:15 1 -> /dev/null
lrwx------ 1 shell shell 64 1970-04-17 12:15 2 -> /dev/null
$
[1] + Terminated \sleep 100 <&- >&- 2>&-
Actual:
$ sleep 100 <&- >&- 2>&- & BGPID=$! && ls -la /proc/$BGPID/fd && kill $BGPID
[1] 16345
total 0
dr-x------ 2 shell shell 0 2019-02-28 20:22 .
dr-xr-xr-x 9 shell shell 0 2019-02-28 20:22 ..
$
[1] + Terminated \sleep 100 <&- >&- 2>&-
Test: manual (see above)
Change-Id: I3e05700a1e8ebc7fc9d192211dd9fc030cc40139
Instead of passing the address of a KernelArgumentBlock to libc.so for
initialization, use __loader_shared_globals() to initialize globals.
Most of the work happened in the previous CLs. This CL switches a few
KernelArgumentBlock::getauxval calls to [__bionic_]getauxval and stops
routing the KernelArgumentBlock address through the libc init functions.
Bug: none
Test: bionic unit tests
Change-Id: I96c7b02c21d55c454558b7a5a9243c682782f2dd
Merged-In: I96c7b02c21d55c454558b7a5a9243c682782f2dd
(cherry picked from commit 746ad15912)
Make getauxval() work in .preinit_array. It still won't be usable for
ifuncs unless we can guarantee that the __loader_shared_globals relocation
is resolved before the ifunc calls [__bionic_]getauxval.
Define __bionic_getauxval for use in replacing calls to
KernelArgumentBlock::getauxval, which doesn't (and sometimes isn't allowed
to) access TLS variables like errno.
Bug: http://b/25751302
Test: bionic unit tests
Change-Id: I461feeaed7f43cfa2a2b6c34147194f0df82b516
Merged-In: I461feeaed7f43cfa2a2b6c34147194f0df82b516
(cherry picked from commit bdab4a2b97)
Initialize the __progname and environ global variables using
libc_shared_globals rather than KernelArgumentBlock.
Also: suppose the linker is invoked on an executable:
linker prog [args...]
The first argument passed to main() and constructor functions is "prog"
rather than "linker". For consistency, this CL changes the BSD
__progname global from "linker" to "prog".
Bug: none
Test: bionic unit tests
Change-Id: I376d76953c9436706dbc53911ef6585c1acc1c31
__libc_shared_globals() is available in dynamic modules as soon as
relocation has finished (i.e. after ifuncs run). Before ifuncs have run,
the android_set_abort_message() function already doesn't work because it
calls public APIs via the PLT. (If this matters, we can use a static
bool variable to enable android_set_abort_message after libc
initialization).
__libc_shared_globals() is hidden, so it's available in the linker
immediately (i.e. before relocation). TLS memory (e.g. errno) currently
isn't accessible until after relocation, but a later patch fixes that.
Bug: none
Test: bionic unit tests
Change-Id: Ied4433758ed2da9ee404c6158e319cf502d05a53
Previously, the address of the global variable was communicated from the
dynamic linker to libc.so using a field of KernelArgumentBlock, which is
communicated using the TLS_SLOT_BIONIC_PREINIT slot.
As long as this function isn't called during relocations (i.e. while
executing an ifunc), it always return a non-NULL value. If it's called
before its PLT entry is relocated, I expect a crash.
I removed the __libc_init_shared_globals function. It's currently empty,
and I don't think there's one point in libc's initialization where
shared globals should be initialized.
Bug: http://b/25751302
Test: bionic unit tests
Change-Id: I614d25e7ef5e0d2ccc40d5c821dee10f1ec61c2e
__sanitize_environment_variables is only called when getauxval(AT_SECURE)
is true.
Instead of scanning __libc_auxv, reuse getauxval. If the entry is missing,
getauxval will set errno to ENOENT.
Reduce the number of times that __libc_sysinfo and __libc_auxv are
initialized. (Previously, __libc_sysinfo was initialized 3 times for the
linker's copy). The two variables are initialized in these places:
- __libc_init_main_thread for libc.a (including the linker copy)
- __libc_preinit_impl for libc.so
- __linker_init: the linker's copy of __libc_sysinfo is still initialized
twice, because __libc_init_main_thread runs after relocation. A later
CL consolidates the linker's two initializations.
Bug: none
Test: bionic unit tests
Change-Id: I196f4c9011b0d803ee85c07afb415fcb146f4d65
Add two functions to allow objects that own a file descriptor to
enforce that only they can close their file descriptor.
Use them in FILE* and DIR*.
Bug: http://b/110100358
Test: bionic_unit_tests
Test: aosp/master boots without errors
Test: treehugger
Change-Id: Iecd6e8b26c62217271e0822dc3d2d7888b091a45
__libc_sysinfo is hidden, so accessing it doesn't require a relocated GOT.
It is important not to have a relocatable initializer on __libc_sysinfo,
because if it did have one, and if we initialized it before relocating the
linker, then on 32-bit x86 (which uses REL rather than RELA), the
relocation step would calculate the wrong addend and overwrite
__libc_sysinfo with garbage.
Asides:
* It'd be simpler to keep the __libc_sysinfo initializer for static
executables, but the loader pulls in libc_init_static (even though it
uses almost none of the code in that file, like __libc_init).
* The loader has called __libc_init_sysinfo three times by the time it
has relocated itself. A static executable calls it twice, while libc.so
calls it only once.
Bug: none
Test: lunch aosp_x86-userdebug ; emulator
Test: adb shell /data/nativetest/bionic-unit-tests/bionic-unit-tests
Test: adb shell /data/nativetest/bionic-unit-tests-static/bionic-unit-tests-static
Change-Id: I5944f57847db7191608f4f83dde22b49e279e6cb
This complements __libc_init_main_thread in setting up main thread
under native bridge.
Test: run_tests
Bug: 77877742
Change-Id: I53efab66f285a1b9f0ab36d44386fa1e2621e4ba
(cherry picked from commit 4c9504aa6c)
This library is used by a number of different libraries in the system.
Make it easy for platform libraries to use this library and create
an actual exported include file.
Change the names of the functions to reflect the new name of the library.
Run clang_format on the async_safe_log.cpp file since the formatting is
all over the place.
Bug: 31919199
Test: Compiled for angler/bullhead, and booted.
Test: Ran bionic unit tests.
Test: Ran the malloc debug tests.
Change-Id: I8071bf690c17b0ea3bc8dc5749cdd5b6ad58478a
For security reasons, when a binary is executed which causes a security
transition (eg, a setuid binary, setgid binary, filesystem capabilities,
or SELinux domain transition), the AT_SECURE flag is set. This causes
certain blacklisted environment variables to be stripped before the
process is executed. The list of blacklisted environment variables is
stored in UNSAFE_VARIABLE_NAMES. Generally speaking, most environment
variables used internally by libc show up in this list.
Add ANDROID_DNS_MODE to the list of unsafe variables.
Similar to RESOLV_HOST_CONF and RES_OPTIONS (which are already
blacklisted), this variable controls how name resolution requests are
handled. Allowing ANDROID_DNS_MODE to be set across a security
boundary could induce resolution failures or otherwise impact
name resolution.
Remove BIONIC_DNSCACHE. This does not appear to be used, and setting
this variable across a security boundary could cause name resolution
problems.
Test: Android compiles and runs with no obvious problems.
Change-Id: I835a7b42d6afbc9c67866594c7951cfd9b355d81
Used by CFI, so broke cfi_test#early_init@x86, but I've added a specific
test for this (and a similar test for getauxval from preinit, which this
patch does not fix).
Bug: http://b/35885875
Test: ran tests
Change-Id: I43885bedfb88c0a26b4474bd3c27a87dec7bbc97
Another release, another attempt to fix this bug.
This change affects pthread_detach, pthread_getcpuclockid,
pthread_getschedparam/pthread_setschedparam, pthread_join, and pthread_kill:
instead of returning ESRCH when passed an invalid pthread_t, they'll now SEGV.
Note that this doesn't change behavior as much as you might think: the old
lookup only held the global thread list lock for the duration of the lookup,
so there was still a race between that and the dereference in the caller,
given that callers actually need the tid to pass to some syscall or other,
and sometimes update fields in the pthread_internal_t struct too.
We can't check thread->tid against 0 to see whether a pthread_t is still
valid because a dead thread gets its thread struct unmapped along with its
stack, so the dereference isn't safe.
Taking the affected functions one by one:
* pthread_getcpuclockid and pthread_getschedparam/pthread_setschedparam
should be fine. Unsafe calls to those seem highly unlikely.
* Unsafe pthread_detach callers probably want to switch to
pthread_attr_setdetachstate instead, or using pthread_detach(pthread_self())
from the new thread's start routine rather than doing the detach in the
parent.
* pthread_join calls should be safe anyway, because a joinable thread won't
actually exit and unmap until it's joined. If you're joining an
unjoinable thread, the fix is to stop marking it detached. If you're
joining an already-joined thread, you need to rethink your design.
* Unsafe pthread_kill calls aren't portably fixable. (And are obviously
inherently non-portable as-is.) The best alternative on Android is to
use pthread_gettid_np at some point that you know the thread to be alive,
and then call kill/tgkill directly. That's still not completely safe
because if you're too late, the tid may have been reused, but then your
code is inherently unsafe anyway.
If we find too much code is still broken, we can come back and disable
the global thread list lookups for anything targeting >= O and then have
another go at really removing this in P...
Bug: http://b/19636317
Test: N6P boots, bionic tests pass
Change-Id: Ia92641212f509344b99ee2a9bfab5383147fcba6
The linker calls to __libc_fatal resulted in tombstones
with missing abort message. This commit fixes it by
initializing __abort_message_ptr for the linker's copy
of libc.
Bug: http://b/31095185
Change-Id: I883d654d7fd0ef309c80f8021202b6bfd5d5cea5
Before, dynamic executables would initialize the global stack protector
twice, once for the linker, and once for the executable. This worked
because the result was the same for both initializations, because it
used getauxval(AT_RANDOM), which won't be the case once arc4random gets
used for it.
Bug: http://b/29622562
Change-Id: I7718b1ba8ee8fac7127ab2360cb1088e510fef5c
Test: ran the stack protector tests on angler (32/64bit, static/dynamic)
Previously, arc4random would register a fork-detecting pthread_atfork
handler to not have to call getpid() after a fork. pthread_atfork uses
pthread_mutex_lock, which requires the current thread to be initialized,
preventing the use of arc4random for initializing the global stack guard,
which needs to happen before the main thread has been initialized.
Extract the arc4random fork-detection flag and use the existing
arc4random fork handler to set it.
Bug: http://b/29622562
Change-Id: I98c9329fa0e489c3f78cad52747eaaf2f5226b80
Although there is a test pthread.pthread_mutex_owner_tid_limit
to check pid_max, but bionic-unit-tests hangs before reaching
that test. So abort at libc initialization if not able to reach
the test when running bionic-unit-tests32. It is more friendly
for debugging.
Bug: 24016357
Change-Id: Ia70c2e36fd8a3a040d41ea5722c7b48a6134e102
This patch uses __kernel_vsyscall instead of "int 0x80"
as the syscall entry point. AT_SYSINFO points to
an adapter to mask the arch specific difference and gives a
performance boost on i386 architecture.
Change-ID: Ib340c604d02c6c25714a95793737e3cfdc3fc5d7
Signed-off-by: Mingwei Shi <mingwei.shi@intel.com>
The major components of the rewrite:
- Completely remove the qemu shared library code. Nobody was using it
and it appears to have broken at some point.
- Adds the ability to enable/disable different options independently.
- Adds a new option that can enable the backtrace on alloc/free when
a process gets a specific signal.
- Adds a new way to enable malloc debug. If a special property is
set, and the process has an environment variable set, then debug
malloc will be enabled. This allows something that might be
a derivative of app_process to be started with an environment variable
being enabled.
- get_malloc_leak_info() used to return one element for each pointer that
had the exact same backtrace. The new version returns information for
every one of the pointers with same backtrace. It turns out ddms already
automatically coalesces these, so the old method simply hid the fact
that there where multiple pointers with the same amount of backtrace.
- Moved all of the malloc debug specific code into the library.
Nothing related to the malloc debug data structures remains in libc.
- Removed the calls to the debug malloc cleanup routine. Instead, I
added an atexit call with the debug malloc cleanup routine. This gets
around most problems related to the timing of doing the cleanup.
The new properties and environment variables:
libc.debug.malloc.options
Set by option name (such as "backtrace"). Setting this to a bad value
will cause a usage statement to be printed to the log.
libc.debug.malloc.program
Same as before. If this is set, then only the program named will
be launched with malloc debug enabled. This is not a complete match,
but if any part of the property is in the program name, malloc debug is
enabled.
libc.debug.malloc.env_enabled
If set, then malloc debug is only enabled if the running process has the
environment variable LIBC_DEBUG_MALLOC_ENABLE set.
Bug: 19145921
Change-Id: I7b0e58cc85cc6d4118173fe1f8627a391b64c0d7
Exactly which functions get a stack protector is up to the compiler, so
let's separate the code that sets up the environment stack protection
requires and explicitly build it with -fno-stack-protector.
Bug: http://b/26276517
Change-Id: I8719e23ead1f1e81715c32c1335da868f68369b5
We need to ensure %gs:20 is set up early enough for -fstack-protector-strong
on x86, and that __set_tls doesn't get stack protector checks because it's a
prerequisite for them. x86 devices/emulators won't boot without this.
Bug: http://b/26073874
Change-Id: Icf0d34294648cc0c8cb406a3617befe0d45c525a
This reverts commit c8bae05f3f.
We were breaking init (ueventd) because we initialize system properties
before we initialize stdio. The new system property implementation uses
stdio to read from /property_contexts, so we end up touching stdio data
structures before they've been initialized.
This second attempt takes things further by removing the stdio initialization
function altogether. The data structures for stdin/stdout/stderr can be
statically initialized as data, and -- since we already had to give the
atexit implementation a backdoor for stdio -- we can just admit that we
need to clean up stdio, and that we always do so last.
This patch also removes the 17 statically pre-allocated file structures,
so the first fopen will now allocate a block of 10 (the usual overflow
behavior). I did this just to make my life simpler, but it's not actually
necessary to remove it if we want it back.
Change-Id: I936b2eb5e88e4ebaf5516121872b71fc88e5609c
This reverts commit 4371961e00.
This broke booting; ueventd crashes with a null pointer dereference
somewhere in __sfp (but the kernel doesn't unwind, so I don't know
what was calling __sfp).
Change-Id: I65375fdfdf1d339a06558b4057b580cacd6324e2
Previously we call __sinit() lazily. But it is likely to cause data
races like in https://android-review.googlesource.com/#/c/183237/. So
we prefer to call __sinit() explicitly at libc initialization.
Bug: 25392375
Change-Id: I181ea7a4b2e4c7350b45f2e6c86886ea023e80b8
If tsan is used, the following callchain can happen:
__libc_preinit() -> __libc_init_globals() ->
__libc_init_vdso() -> strcmp() -> __tsan_init()
-> sysconf(_SC_PAGE_SIZE) -> getauxval().
But __libc_auxv is initialized in __libc_init_common(),
after __libc_init_globals(). One simple way to fix
this is to initialize __libc_auxv at __libc_init_globals().
Bug: 25392375
Change-Id: I3893b1f567d5f3b7a8c881c0c1b8234b06b7751b
The current comment implies that we only strip sensitive
environment variables on executing a setuid program. This is
true but incomplete. The AT_SECURE flag is set whenever a
security transition occurs, such as executing a setuid program,
SELinux security transition, executing a file with file capabilities,
etc...
Fixup the comments.
Change-Id: I30a73992adfde14d6e5f642b3a1ead2ee56726be
Reuse the top bits of _JB_SIGFLAG field previously used to store a
boolean to store a cookie that's validated by [sig]longjmp to make it
harder to use as a ROP gadget. Additionally, encrypt saved registers
with the cookie so that an attacker can't modify a register's value to
a specific value without knowing the cookie.
Bug: http://b/23942752
Change-Id: Id0eb8d06916e89d5d776bfcaa9458f8826717ba3
1. Personality parameter should be unsigned int (not long)
2. Do not reset bits outside of PER_MASK when setting
personality value.
3. Set personality for static executables.
Bug: http://b/21900686
Change-Id: I4c7e34079cbd59b818ce221eed325c05b9bb2303
(cherry picked from commit f643eb38c3)
As glibc/netbsd don't protect access to thread struct members by a global
lock, we don't want to do it either. This change reduces the
responsibility of g_thread_list_lock to only protect g_thread_list.
Bug: 19636317
Change-Id: I897890710653dac165d8fa4452c7ecf74abdbf2b
Make this change because I think it is more reasonable to check stack info
in pthread_getattr_np. I believe pthread_attr_t is not tied with any thread,
and can't have a flag saying who using it is the main thread.
This change also helps refactor of g_thread_list_lock.
Bug: 19636317
Change-Id: Iedbb85a391ac3e1849dd036d01445dac4bc63db9
