For instance, the read wrapper is currently expanded as:
extern __inline
__attribute__((__always_inline__))
__attribute__((__artificial__))
__attribute__((__warn_unused_result__))
ssize_t read (int __fd, void *__buf, size_t __nbytes)
{
return __glibc_safe_or_unknown_len (__nbytes,
sizeof (char),
__glibc_objsize0 (__buf))
? __read_alias (__fd, __buf, __nbytes)
: __glibc_unsafe_len (__nbytes,
sizeof (char),
__glibc_objsize0 (__buf))
? __read_chk_warn (__fd,
__buf,
__nbytes,
__builtin_object_size (__buf, 0))
: __read_chk (__fd,
__buf,
__nbytes,
__builtin_object_size (__buf, 0));
}
The wrapper relies on __builtin_object_size call lowers to a constant at
compile-time and many other operations in the wrapper depends on
having a single, known value for parameters. Because this is
impossible to have for function parameters, the wrapper depends heavily
on inlining to work and While this is an entirely viable approach on
GCC, it is not fully reliable on clang. This is because by the time llvm
gets to inlining and optimizing, there is a minimal reliable source and
type-level information available (more information on a more deep
explanation on how to fortify wrapper works on clang [1]).
To allow the wrapper to work reliably and with the same functionality as
with GCC, clang requires a different approach:
* __attribute__((diagnose_if(c, “str”, “warning”))) which is a function
level attribute; if the compiler can determine that 'c' is true at
compile-time, it will emit a warning with the text 'str1'. If it would
be better to emit an error, the wrapper can use "error" instead of
"warning".
* __attribute__((overloadable)) which is also a function-level attribute;
and it allows C++-style overloading to occur on C functions.
* __attribute__((pass_object_size(n))) which is a parameter-level
attribute; and it makes the compiler evaluate
__builtin_object_size(param, n) at each call site of the function
that has the parameter, and passes it in as a hidden parameter.
This attribute has two side-effects that are key to how FORTIFY works:
1. It can overload solely on pass_object_size (e.g. there are two
overloads of foo in
void foo(char * __attribute__((pass_object_size(0))) c);
void foo(char *);
(The one with pass_object_size attribute has precende over the
default one).
2. A function with at least one pass_object_size parameter can never
have its address taken (and overload resolution respects this).
Thus the read wrapper can be implemented as follows, without
hindering any fortify coverage compile and runtime:
extern __inline
__attribute__((__always_inline__))
__attribute__((__artificial__))
__attribute__((__overloadable__))
__attribute__((__warn_unused_result__))
ssize_t read (int __fd,
void *const __attribute__((pass_object_size (0))) __buf,
size_t __nbytes)
__attribute__((__diagnose_if__ ((((__builtin_object_size (__buf, 0)) != -1ULL
&& (__nbytes) > (__builtin_object_size (__buf, 0)) / (1))),
"read called with bigger length than size of the destination buffer",
"warning")))
{
return (__builtin_object_size (__buf, 0) == (size_t) -1)
? __read_alias (__fd,
__buf,
__nbytes)
: __read_chk (__fd,
__buf,
__nbytes,
__builtin_object_size (__buf, 0));
}
To avoid changing the current semantic for GCC, a set of macros is
defined to enable the clang required attributes, along with some changes
on internal macros to avoid the need to issue the symbol_chk symbols
(which are done through the __diagnose_if__ attribute for clang).
The read wrapper is simplified as:
__fortify_function __attribute_overloadable__ __wur
ssize_t read (int __fd,
__fortify_clang_overload_arg0 (void *, ,__buf),
size_t __nbytes)
__fortify_clang_warning_only_if_bos0_lt (__nbytes, __buf,
"read called with bigger length than "
"size of the destination buffer")
{
return __glibc_fortify (read, __nbytes, sizeof (char),
__glibc_objsize0 (__buf),
__fd, __buf, __nbytes);
}
There is no expected semantic or code change when using GCC.
Also, clang does not support __va_arg_pack, so variadic functions are
expanded to call va_arg implementations. The error function must not
have bodies (address takes are expanded to nonfortified calls), and
with the __fortify_function compiler might still create a body with the
C++ mangling name (due to the overload attribute). In this case, the
function is defined with __fortify_function_error_function macro
instead.
[1] https://docs.google.com/document/d/1DFfZDICTbL7RqS74wJVIJ-YnjQOj1SaoqfhbgddFYSM/edit
Checked on aarch64, armhf, x86_64, and i686.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
__vsyslog_internal calculated a buffer size by adding two integers, but
did not first check if the addition would overflow. This commit fixes
that.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
__vsyslog_internal used the return value of snprintf/vsnprintf to
calculate buffer sizes for memory allocation. If these functions (for
any reason) failed and returned -1, the resulting buffer would be too
small to hold output. This commit fixes that.
All snprintf/vsnprintf calls are checked for negative return values and
the function silently returns upon encountering them.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
__vsyslog_internal did not handle a case where printing a SYSLOG_HEADER
containing a long program name failed to update the required buffer
size, leading to the allocation and overflow of a too-small buffer on
the heap. This commit fixes that. It also adds a new regression test
that uses glibc.malloc.check.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
This restore the 2.33 semantic for arena_get2. It was changed by
11a02b035b to avoid arena_get2 call malloc (back when __get_nproc
was refactored to use an scratch_buffer - 903bc7dcc2). The
__get_nproc was refactored over then and now it also avoid to call
malloc.
The 11a02b035b did not take in consideration any performance
implication, which should have been discussed properly. The
__get_nprocs_sched is still used as a fallback mechanism if procfs
and sysfs is not acessible.
Checked on x86_64-linux-gnu.
Reviewed-by: DJ Delorie <dj@redhat.com>
This allows to include bits/syslog-decl.h in include/sys/syslog.h and
therefore be able to create the libc_hidden_builtin_proto (__syslog_chk)
prototype.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
The __fdelt_chk declaration needs to be available so that
libc_hidden_proto can be used while not redefining __FD_ELT.
Thus, misc/bits/select-decl.h is created to hold the corresponding
prototypes.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
The __REDIRECT* macros are creating aliases which may lead to unwanted
PLT entries when fortification is enabled.
To prevent these entries, the REDIRECT alias should be set to point to the
existing __GI_* aliases.
This is done transparently by creating a __REDIRECT_FORTIFY* version of
these macros, that can be overwritten internally when necessary.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
Since the _FORTIFY_SOURCE feature uses some routines of Glibc, they need to
be excluded from the fortification.
On top of that:
- some tests explicitly verify that some level of fortification works
appropriately, we therefore shouldn't modify the level set for them.
- some objects need to be build with optimization disabled, which
prevents _FORTIFY_SOURCE to be used for them.
Assembler files that implement architecture specific versions of the
fortified routines were not excluded from _FORTIFY_SOURCE as there is no
C header included that would impact their behavior.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
With fortification enabled, few function calls return result need to be
checked, has they get the __wur macro enabled.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
With fortification enabled, few function calls return result need to be
checked, has they get the __wur macro enabled.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
Reflow Makefile.
Sort using updated scripts/sort-makefile-lines.py.
Code generation is changed as routines are linked in sorted order
as expected.
No regressions on x86_64 and i686.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
Reflow Makefile.
Sort using scripts/sort-makefile-lines.py.
Code generation is changed as routines are linked in sorted order
as expected.
No regressions on x86_64 and i686.
This patch redirects the error functions to the appropriate
longdouble variants which enables the compiler to optimize
for the abi ieeelongdouble.
Signed-off-by: Sachin Monga <smonga@linux.ibm.com>
GCC docs explicitly list perror () as a good candidate for using
__attribute__ ((cold)). So apply __COLD to perror () and similar
functions.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20230429131223.2507236-3-bugaevc@gmail.com>
This expands to __attribute__ ((cold)) when supported. It should be
used to mark up functions that are invoked rarely.
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
This is nicer, and is going to be required for the following changes
to reasonably stay within the 79 column limit.
No functional change.
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Message-Id: <20230419160207.65988-2-bugaevc@gmail.com>
They are both used by __libc_freeres to free all library malloc
allocated resources to help tooling like mtrace or valgrind with
memory leak tracking.
The current scheme uses assembly markers and linker script entries
to consolidate the free routine function pointers in the RELRO segment
and to be freed buffers in BSS.
This patch changes it to use specific free functions for
libc_freeres_ptrs buffers and call the function pointer array directly
with call_function_static_weak.
It allows the removal of both the internal macros and the linker
script sections.
Checked on x86_64-linux-gnu, i686-linux-gnu, and aarch64-linux-gnu.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Define the __glibc_fortify and other macros only when __FORTIFY_LEVEL >
0. This has the effect of not defining these macros on older C90
compilers that do not have support for variable length argument lists.
Also trim off the trailing backslashes from the definition of
__glibc_fortify and __glibc_fortify_n macros.
Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
Reviewed-by: Florian Weimer <fweimer@redhat.com>
Similar to d0fa09a770, but for syslog.h when _FORTIFY_SOURCE > 0.
Fixes [BZ #27087] by applying long double-related asm redirections
before using functions in bits/syslog.h.
Tested with build-many-glibcs.py.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
clang emits an warning when a double alias redirection is used, to warn
the the original symbol will be used even when weak definition is
overridden. However, this is a common pattern for weak_alias, where
multiple alias are set to same symbol.
Reviewed-by: Fangrui Song <maskray@google.com>
In the future, this will result in a compilation failure if the
macros are unexpectedly undefined (due to header inclusion ordering
or header inclusion missing altogether).
Assembler sources are more difficult to convert. In many cases,
they are hand-optimized for the mangling and no-mangling variants,
which is why they are not converted.
sysdeps/s390/s390-32/__longjmp.c and sysdeps/s390/s390-64/__longjmp.c
are special: These are C sources, but most of the implementation is
in assembler, so the PTR_DEMANGLE macro has to be undefined in some
cases, to match the assembler style.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
This allows us to define a generic no-op version of PTR_MANGLE and
PTR_DEMANGLE. In the future, we can use PTR_MANGLE and PTR_DEMANGLE
unconditionally in C sources, avoiding an unintended loss of hardening
due to missing include files or unlucky header inclusion ordering.
In i386 and x86_64, we can avoid a <tls.h> dependency in the C
code by using the computed constant from <tcb-offsets.h>. <sysdep.h>
no longer includes these definitions, so there is no cyclic dependency
anymore when computing the <tcb-offsets.h> constants.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The a583b6add4 change did not handle large messages that
would require a heap allocation correctly, where the message itself
is not take in consideration.
This patch fixes it and extend the tst-syslog to check for large
messages as well.
Checked on x86_64-linux-gnu.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
By adding an internal alias to avoid the GOT indirection.
On some architecture, __libc_single_thread may be accessed through
copy relocations and thus it requires to update also the copies
default copy.
This is done by adding a new internal macro,
libc_hidden_data_{proto,def}, which has an addition argument that
specifies the alias name (instead of default __GI_ one).
Checked on x86_64-linux-gnu and i686-linux-gnu.
Reviewed-by: Fangrui Song <maskray@google.com>
It was added on Linux 5.10 (ecb8ac8b1f146915aa6b96449b66dd48984caacc)
with the same functionality as madvise but using a pidfd of the target
process.
Checked on x86_64-linux-gnu and i686-linux-gnu.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
The check for an ISO C compiler assumes that anything GCC-like will
define __STDC__, even if it's actually a C++ compiler. That's currently
true for G++ and compilers like clang++ that also define __GNUC__, but
it might not always be true.
The C++ standard leaves it implementation-defined whether or not
__STDC__ is defined by C++ compilers. And really the check should be
"ISO C or ISO C++ conforming compiler" anyway. So only give an error if
__GNUC__ is defined and neither __STDC__ nor __cplusplus is defined.
Reviewed-by: Fangrui Song <maskray@google.com>
The fix c8ee1c85 introduced a -1 check for object size without also
checking that object size is a constant. Because of this, the tree
optimizer passes in gcc fail to fold away one of the branches in
__glibc_fortify and trips on a spurious Wstringop-overflow. The warning
itself is incorrect and the branch does go away eventually in DCE in the
rtl passes in gcc, but the constant check is a helpful hint to simplify
code early, so add it in.
Resolves: BZ #29141
Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
If `__glibc_objsize (__o) == (size_t) -1` (i.e. `__o` is unknown size), fortify
checks should pass, and `__whatever_alias` should be called.
Previously, `__glibc_objsize (__o) == (size_t) -1` was explicitly checked, but
on commit a643f60c53, this was moved into `__glibc_safe_or_unknown_len`.
A comment says the -1 case should work as: "The -1 check is redundant because
since it implies that __glibc_safe_len_cond is true.". But this fails when:
* `__s > 1`
* `__osz == -1` (i.e. unknown size at compile time)
* `__l` is big enough
* `__l * __s <= __osz` can be folded to a constant
(I only found this to be true for `mbsrtowcs` and other functions in wchar2.h)
In this case `__l * __s <= __osz` is false, and `__whatever_chk_warn` will be
called by `__glibc_fortify` or `__glibc_fortify_n` and crash the program.
This commit adds the explicit `__osz == -1` check again.
moc crashes on startup due to this, see: https://bugs.archlinux.org/task/74041
Minimal test case (test.c):
#include <wchar.h>
int main (void)
{
const char *hw = "HelloWorld";
mbsrtowcs (NULL, &hw, (size_t)-1, NULL);
return 0;
}
Build with:
gcc -O2 -Wp,-D_FORTIFY_SOURCE=2 test.c -o test && ./test
Output:
*** buffer overflow detected ***: terminated
Fixes: BZ #29030
Signed-off-by: Joan Bruguera <joanbrugueram@gmail.com>
Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
It also handles the highly unlikely case where localtime might return
NULL, in this case only the PRI is set to hopefully instruct the relay
to get eh TIMESTAMP (as defined by the RFC).
Checked on x86_64-linux-gnu and i686-linux-gnu.
There is no easy solution as described on first comment in bug report,
and some code (like busybox) assumes facilitynames existance when
SYSLOG_NAMES is defined (so we can't just remove it as suggested in
comment #2).
So use the easier solution and guard it with __USE_MISC.
A fixed-sized buffer is used instead of memstream for messages up to
1024 bytes to avoid the potential BUFSIZ (8K) malloc and free for
each syslog call.
Also, since the buffer size is know, memstream is replaced with a
malloced buffer for larger messages.
Checked on x86_64-linux-gnu.
Use a temporary buffer for strftime instead of using internal libio
members, simplify fprintf call on the memstream and memory allocation,
use %b instead of %h, use dprintf instead of writev for LOG_PERROR.
Checked on x86_64-linux-gnu and i686-linux-gnu.
The test cover:
- All possible priorities and facilities through TCP and UDP.
- Same syslog tests for vsyslog.
- Some openlog/syslog/close combinations.
- openlog with LOG_CONS, LOG_PERROR, and LOG_PID.
Internally is done with a test-container where the main process mimics
the syslog server interface.
The test does not cover multithread and async-signal usage.
Checked on x86_64-linux-gnu.
This patch adds some missing access function attributes to getrandom /
getentropy and several functions in sys/xattr.h
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
gcc 12 now has support for the __builtin_dynamic_object_size builtin.
Adapt the macro checks to enable _FORTIFY_SOURCE=3 on gcc 12 and above.
Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
I used these shell commands:
../glibc/scripts/update-copyrights $PWD/../gnulib/build-aux/update-copyright
(cd ../glibc && git commit -am"[this commit message]")
and then ignored the output, which consisted lines saying "FOO: warning:
copyright statement not found" for each of 7061 files FOO.
I then removed trailing white space from math/tgmath.h,
support/tst-support-open-dev-null-range.c, and
sysdeps/x86_64/multiarch/strlen-vec.S, to work around the following
obscure pre-commit check failure diagnostics from Savannah. I don't
know why I run into these diagnostics whereas others evidently do not.
remote: *** 912-#endif
remote: *** 913:
remote: *** 914-
remote: *** error: lines with trailing whitespace found
...
remote: *** error: sysdeps/unix/sysv/linux/statx_cp.c: trailing lines
Starting with commit b05fae4d8e
"elf: Use the minimal malloc on tunables_strdup",
I get lots of segfaults in static tests on s390x when also using, e.g.:
export GLIBC_TUNABLES="glibc.elision.enable=1"
tunables_strdup callls __minimal_malloc which tries to call __mmap
due to insufficient space left. __mmap itself first setups a new
stack frame and segfaults when copying the stack-protector canary
from thread-pointer. The latter one is not yet setup.
Thus this patch also turns off stack-protection for mmap.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
The function was renamed to __atomic_wide_counter_load_relaxed
in commit 8bd336a00a ("nptl: Extract
<bits/atomic_wide_counter.h> from pthread_cond_common.c").
And make it an installed header. This addresses a few aliasing
violations (which do not seem to result in miscompilation due to
the use of atomics), and also enables use of wide counters in other
parts of the library.
The debug output in nptl/tst-cond22 has been adjusted to print
the 32-bit values instead because it avoids a big-endian/little-endian
difference.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
