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linux commit 2200aa7154cb7ef76bac93e98326883ba64bfa2e
arm64: mte: ptrace: Add NT_ARM_TAGGED_ADDR_CTRL regset
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linux commit e47168f3d1b14af5281cf50c59561d59d28201f9
powerpc/8xx: Support 16k hugepages with 4k pages
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path resolution does not follow symlinks on nosymfollow mounts (but
readlink still does), see
linux commit dab741e0e02bd3c4f5e2e97be74b39df2523fc6e
Add a "nosymfollow" mount option.
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can cause rseq restart on another cpu to synchronize with global
memory access from rseq critical sections, see
linux commit 2a36ab717e8fe678d98f81c14a0b124712719840
rseq/membarrier: Add MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ
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mainly added to linux to allow a central process management service in
android to give MADV_COLD|PAGEOUT hints for other processes, see
linux commit ecb8ac8b1f146915aa6b96449b66dd48984caacc
mm/madvise: introduce process_madvise() syscall: an external memory
hinting API
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the historical function was specified to return an empty string in the
caller-provided buffer, not a null pointer, to indicate error when the
argument is non-null. only when the argument is null should it return
a null pointer on error.
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getpwuid_r can return 0 but without a result in the case where there
was no error but no record exists. in that case cuserid was treating
it as success and copying junk out of pw.pw_name to the output buffer.
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checking the length also drops the need to pull in snprintf.
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this function was removed from the standard in 2001 but appeared in
SUSv2 with an obligation to support calls with a null pointer
argument, using a static buffer.
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ELF_NFPREG is used by some userspace applications like gdb
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the threshold was wrong so expm1f overflowed to inf a bit too early
and on most targets uint32_t compare is faster than float compare so
use that.
this also fixes sinhf incorrectly returning nan for some values where
the internal expm1f overflowed.
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on some negative inputs (e.g. -0x1.1e6ae8p+5) acoshf failed to return
nan. ensure that negative inputs result nan without introducing new
branches. this was tried before in
commit 101e6012856918440b5d7474739c3fc22a8d3b85
math: fix acoshf on negative values
but that fix was wrong. there are 3 formulas used:
log1p(x-1 + sqrt((x-1)*(x-1)+2*(x-1)))
log(2*x - 1/(x+sqrt(x*x-1)))
log(x) + 0.693147180559945309417232121458176568
the first fails on large negative inputs (may compute log1p(0) or
log1p(inf)), the second one fails on some mid range or large negative
inputs (may compute log(large) or log(inf)) and the last one fails on
-0 (returns -inf).
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the omission of the flag here seems to have been an oversight when the
function was added in 8fb28b0b3e7a5e958fb844722a4b2ef9bc244af1
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as an outcome of Austin Group issue #385, future versions of the
standard will require free not to alter the value of errno. save and
restore it individually around the calls to madvise and munmap so that
the cost is not imposed on calls to free that do not result in any
syscall.
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commit 8d37958d58cf36f53d5fcc7a8aa6d633da6071b2 inadvertently broke
oldmalloc by having it implement __libc_malloc rather than
__libc_malloc_impl.
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as an outcome of Austin Group issue #385, future versions of the
standard will require free not to alter the value of errno. save and
restore it individually around the calls to madvise and munmap so that
the cost is not imposed on calls to free that do not result in any
syscall.
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commit 7586360badcae6e73f04eb1b8189ce630281c4b2 removed the unused
arguments from the definition of __libc_start_main, making it
incompatible with the declaration at the point of call, which still
passed 6 arguments. calls with mismatched function type have undefined
behavior, breaking LTO and any other tooling that checks for function
signature mismatch.
removing the extra arguments from the point of call (crt1) is not an
option for fixing this, since that would be a change in ABI surface
between application and libc.
adding back the extra arguments requires some care. on archs that pass
arguments on the stack or that reserve argument spill space for the
callee on the stack, it imposes an ABI requirement on the caller to
provide such space. the modern crt1.c entry point provides such space,
but originally there was arch-specific asm for the call to
__libc_start_main. the last of this asm was removed in commit
6fef8cafbd0f6f185897bc87feb1ff66e2e204e1, and manual review of the
code removed and its prior history was performed to check that all
archs/variants passed the legacy init/fini/ldso_fini arguments.
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these functions are specified to fail with EBADF on negative fd
arguments. apart from close, they are also specified to fail if the
value exceeds OPEN_MAX, but as written it is not clear that this
imposes any requirement when OPEN_MAX is not defined, and it's
undesirable to impose a dynamic limit (via setrlimit) here since the
limit at the time of posix_spawn may be different from the limit at
the time of setting up the file actions. this may require revisiting
later.
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commit 2412638bb39eb799b2600393bbd71cca8ae96bb2 got the size of struct
v4l2_event wrong and failed to account for the fact that the old
struct might be either 120 bytes with time misaligned mod 8, or 128
bytes with time aligned mod 8, due to the contained union having
64-bit members whose alignment is arch-dependent.
rather than adding new logic to handle the differences, use an actual
stripped-down version of the structure in question to derive the ioctl
number, size, and offsets.
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commit 2412638bb39eb799b2600393bbd71cca8ae96bb2 got the size of struct
v4l2_buffer wrong and omitted the tv_usec member slot from the offset
list, so the ioctl numbers never matched and fallback code path was
never taken. this caused the affected ioctls to fail with ENOTTY on
kernels not new enough to have the native time64 ioctls.
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while the layouts match, the member member naming expected by software
using mcontext_t omits the sc_ prefix.
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this is necessary for MT-fork correctness now that the code runs under
locale lock. it would not be hard to avoid, but __get_locale is
already using libc-internal malloc anyway. this can be reconsidered
during locale overhaul later if needed.
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in general, pthread_once is not compatible with MT-fork constraints
(commit 167390f05564e0a4d3fcb4329377fd7743267560). here it actually no
longer matters, because it's now called with a lock held, but since
the lock is held it's pointless to use pthread_once.
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this allows the lock to be shared with setlocale, eliminates repeated
per-category lock/unlock in newlocale, and will allow the use of
pthread_once in newlocale to be dropped (to be done separately).
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the intent here is just to scan at least l bytes forward for the end
of the haystack and at least some decent minimum to avoid doing it
over and over if the needle is short, with no need to be precise. the
comment erroneously stated this as an estimate for MIN when it's
actually an estimate for MAX.
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pthread_once is not compatible with MT-fork constraints (commit
167390f05564e0a4d3fcb4329377fd7743267560) and is not needed here
anyway; we already have a lock suitable for initialization.
while changing this, fix a corner case where AT_MINSIGSTKSZ gives a
value that's more than MINSIGSTKSZ but by a margin of less than
2048, thereby causing the size to be reduced. it shouldn't matter but
the intent was to be the larger of a 2048-byte margin over the legacy
fixed minimum stack requirement or a 512-byte margin over the minimum
the kernel reports at runtime.
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this change should have been made when priority inheritance mutex
support was added. if priority protection is also added at some point
the implementation will need to change and will probably no longer be
a simple bit shuffling.
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ucontext.h depends on the internal struct tag name for namespacing
reasons, and the intent was always for it to be consistent across
archs anyway.
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both __clone and __syscall_cp_asm failed to restore the original value
of r6 after using it as a syscall argument register. the extent of
breakage is not known, and in some cases may be mitigated by the only
callers being internal to libc; if they used r6 but no longer needed
its value after the call, they may not have noticed the problem.
however at least posix_spawn (which uses __clone) was observed
returning to the application with the wrong value in r6, leading to
crash.
since the call frame ABI already provides a place to spill registers,
fixing this is just a matter of using it. in __clone, we also
spuriously restore r6 in the child, since the parent branch directly
returns to the caller. this takes the value from an uninitialized slot
of the child's stack, but is harmless since there is no caller to
return to in the child.
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float_t should represent the type that is used to evaluate float
expressions internally. On s390x, float_t is currently set to double.
In contrast, the isa supports single-precision float operations and
compilers by default evaluate float in single precision, which
violates the C standard (sections 5.2.4.2.2 and 7.12 in C11/C17, to be
precise). With -fexcess-precision=standard, gcc evaluates float in
double precision, which aligns with the standard yet at the cost of
added conversion instructions.
gcc-11 will drop the special case to retrofit double precision
behavior for -fexcess-precision=standard so that __FLT_EVAL_METHOD__
will be 0 on s390x in any scenario.
To improve standards compliance and compatibility with future compiler
direction, this patch changes the definition of float_t to be derived
from the compiler's __FLT_EVAL_METHOD__.
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reallocarray is an extension introduced by OpenBSD, which introduces
calloc overflow checking to realloc.
glibc 2.28 introduced support for this function behind _GNU_SOURCE,
while glibc 2.29 allows its usage in _DEFAULT_SOURCE.
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inability to use realpath in chroot/container without procfs access
and at early boot prior to mount of /proc has been an ongoing issue,
and it turns out realpath was one of the last remaining interfaces
that needed procfs for its core functionality. during investigation
while reimplementing, it was determined that there were also serious
problems with the procfs-based implementation. most seriously it was
unsafe on pre-O_PATH kernels, and unlike other places where O_PATH was
used, the unsafety was hard or impossible to fix because O_NOFOLLOW
can't be used (since the whole purpose was to follow symlinks).
the new implementation is a direct one, performing readlink on each
path component to resolve it. an explicit stack, as opposed to
recursion, is used to represent the remaining components to be
processed. the stack starts out holding just the input string, and
reading a link pushes the link contents onto the stack.
unlike many other implementations, this one does not call getcwd
initially for relative pathnames. instead it accumulates initial ..
components to be applied to the working directory if the result is
still a relative path. this avoids calling getcwd (which may fail) at
all when symlink traversal will eventually yield an absolute path. it
also doesn't use any form of stat operation; instead it arranges for
readlink to tell it when a non-directory is used in a context where a
directory is needed. this minimizes the number of syscalls needed,
avoids accessing inodes when the directory table suffices, and reduces
the amount of code pulled in for static linking.
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commit d1507646975cbf6c3e511ba07b193f27f032d108 added support for null
argument in oldmalloc and was overlooked when switching to mallocng.
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The -a and -o operators are obsolescent and not in baseline POSIX.
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calling lutimes with tv=0 is valid if the application wants to set the
timestamps to the current time. this commit makes it so the timespec
struct is populated with values from tv only if tv != 0 and calls
utimensat with times=0 if tv == 0.
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see
linux commit eba75c587e811d3249c8bd50d22bb2266ccd3c0f
icmp: support rfc 4884
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Update fanotify.h, see
linux commit 929943b38daf817f2e6d303ea04401651fc3bc05
fanotify: add support for FAN_REPORT_NAME
linux commit 83b7a59896dd24015a34b7f00027f0ff3747972f
fanotify: add basic support for FAN_REPORT_DIR_FID
linux commit 08b95c338e0c5a96e47f4ca314ea1e7580ecb5d7
fanotify: remove event FAN_DIR_MODIFY
FAN_DIR_MODIFY that was new in v5.7 is now removed from linux uapi,
but kept in musl, so we don't break api, linux cannot reuse the
value anyway.
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see
linux commit 9b4feb630e8e9801603f3cab3a36369e3c1cf88d
arch: wire-up close_range()
linux commit 278a5fbaed89dacd04e9d052f4594ffd0e0585de
open: add close_range()
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Adds two missing personality(2) personas: UNAME26 and FDPIC_FUNCPTRS.
FDPIC_FUNCPTRS was also missing its corresponding PER_LINUX_FDPIC
value.
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"big-engian" should be "big-endian".
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linux fails with EINVAL when a zero buffer size is passed to the
syscall. this is non-conforming because POSIX already defines EINVAL
with a significantly different meaning: the target is not a symlink.
since the request is semantically valid, patch it up by using a dummy
buffer of length one, and truncating the return value to zero if it
succeeds.
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the v1 zoneinfo format with 32-bit time is deprecated. previously, the
v2 parsing code was only used if an exact match for '2' was found in
the version field of the header. this was already incorrect for v3
files (trivial differences from v2 that arguably didn't merit a new
version number anyway) but also failed to be future-proof.
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since commit 38143339646a4ccce8afe298c34467767c899f51, the condition
sizeof(time_t) > 4 is always true, so there is no functional change
being made here. but semantically, the 64-bit tables should always be
preferred now, because upstream zic (zoneinfo compiler) has quietly
switched to emitting empty 32-bit tables by default, and the resulting
backwards-incompatible zoneinfo files will be encountered in the wild.
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commit d26e0774a59bb7245b205bc8e7d8b35cc2037095 moved the detach state
transition at exit before the thread list lock was taken. this
inadvertently allowed pthread_join to race to take the thread list
lock first, and proceed with unmapping of the exiting thread's memory.
we could fix this by just revering the offending commit and instead
performing __vm_wait unconditionally before taking the thread list
lock, but that may be costly. instead, bring back the old DT_EXITING
vs DT_EXITED state distinction that was removed in commit
8f11e6127fe93093f81a52b15bb1537edc3fc8af, and don't transition to
DT_EXITED (a value of 0, which is what pthread_join waits for) until
after the lock has been taken.
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the original wcsnrtombs implementation, which has been largely
untouched since 0.5.0, attempted to build input-length-limiting
conversion on top of wcsrtombs, which only limits output length. as
best I recall, this choice was made out of a mix of disdain over
having yet another variant function to implement (added in POSIX 2008;
not standard C) and preference not to switch things around and
implement the wcsrtombs in terms of the more general new function,
probably over namespace issues. the strategy employed was to impose
output limits that would ensure the input limit wasn't exceeded, then
finish up the tail character-at-a-time. unfortunately, none of that
worked correctly.
first, the logic in the wcsrtombs loop was wrong in that it could
easily get stuck making no forward progress, by imposing an output
limit too small to convert even one character.
the character-at-a-time loop that followed was even worse. it made no
effort to ensure that the converted multibyte character would fit in
the remaining output space, only that there was a nonzero amount of
output space remaining. it also employed an incorrect interpretation
of wcrtomb's interface contract for converting the null character,
thereby failing to act on end of input, and remaining space accounting
was subject to unsigned wrap-around. together these errors allow
unbounded overflow of the destination buffer, controlled by input
length limit and input wchar_t string contents.
given the extent to which this function was broken, it's plausible
that most applications that would have been rendered exploitable were
sufficiently broken not to be usable in the first place. however, it's
also plausible that common (especially ASCII-only) inputs succeeded in
the wcsrtombs loop, which mostly worked, while leaving the wildly
erroneous code in the second loop exposed to particular non-ASCII
inputs.
CVE-2020-28928 has been assigned for this issue.
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after a non-normal-type process-shared mutex is unlocked, it's
immediately available to another thread to lock, unlock, and destroy,
but the first unlocking thread may still have a pointer to it in its
robust_list pending slot. this means, on async process termination,
the kernel may attempt to access and modify the memory that used to
contain the mutex -- memory that may have been reused for some other
purpose after the mutex was destroyed.
setting up for this kind of race to occur is difficult to begin with,
requiring dynamic use of shared memory maps, and actually hitting the
race is very difficult even with a suitable setup. so this is mostly a
theoretical fix, but in any case the cost is very low.
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the __vm_wait operation can delay forward progress arbitrarily long if
a thread holding the lock is interrupted by a signal. in a worst case
this can deadlock. any critical section holding the thread list lock
must respect lock ordering contracts and must not take any lock which
is not AS-safe.
to fix, move the determination of thread joinable/detached state to
take place before the killlock and thread list lock are taken. this
requires reverting the atomic state transition if we determine that
the exiting thread is the last thread and must call exit, but that's
easy to do since it's a single-threaded context with application
signals blocked.
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as the outcome of Austin Group tracker issue #62, future editions of
POSIX have dropped the requirement that fork be AS-safe. this allows
but does not require implementations to synchronize fork with internal
locks and give forked children of multithreaded parents a partly or
fully unrestricted execution environment where they can continue to
use the standard library (per POSIX, they can only portably use
AS-safe functions).
up until recently, taking this allowance did not seem desirable.
however, commit 8ed2bd8bfcb4ea6448afb55a941f4b5b2b0398c0 exposed the
extent to which applications and libraries are depending on the
ability to use malloc and other non-AS-safe interfaces in MT-forked
children, by converting latent very-low-probability catastrophic state
corruption into predictable deadlock. dealing with the fallout has
been a huge burden for users/distros.
while it looks like most of the non-portable usage in applications
could be fixed given sufficient effort, at least some of it seems to
occur in language runtimes which are exposing the ability to run
unrestricted code in the child as part of the contract with the
programmer. any attempt at fixing such contracts is not just a
technical problem but a social one, and is probably not tractable.
this patch extends the fork function to take locks for all libc
singletons in the parent, and release or reset those locks in the
child, so that when the underlying fork operation takes place, the
state protected by these locks is consistent and ready for the child
to use. locking is skipped in the case where the parent is
single-threaded so as not to interfere with legacy AS-safety property
of fork in single-threaded programs. lock order is mostly arbitrary,
but the malloc locks (including bump allocator in case it's used) must
be taken after the locks on any subsystems that might use malloc, and
non-AS-safe locks cannot be taken while the thread list lock is held,
imposing a requirement that it be taken last.
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