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Signed-off-by: Nicolas Iooss <nicolas.iooss@m4x.org>
There are two problems with lookup_common() and therefore
selabel_lookup() and related functions that this patch fixes:
1) A race with the lazy compilation of regexes. Since the struct
regex_data is allocated and assigned immediately to the parent struct
spec, it's possible for a second thread to see that this pointer is
non-NULL before the regex compilation has finished. This typically
results in a -1 return from selabel_lookup() with ENOENT as errno.
This is fixed by adding synchronization in compile_regex().
2) A race with PCRE2 regex_match(). A struct pcre2_match_data is
created once and used for all regex matches for a given regex. This
is problematic if two threads are attempting to evaluate the same
regex simultaneously. This typically results in a successful return
from selabel_lookup() but with an erroneous selabel.
This is fixed by adding a pthread_mutex within regex_match() for
PCRE2. Note, on my system, creating new matchdata takes roughly an
order of magnitude more time than locking a non-contended
pthread_mutex. I don't believe programs will have enough contention
on this lock to justify that cost.
Bug: 63861738
Test: ueventd unit tests
Change-Id: I13bf782d81d0a0b896d444e396f307ad0dbacb6a
Serialized precompiled regular expressins are architecture
dependent when using PCRE2. This patch
- bumps the SELINUX_COMPILED_FCONTEXT version to 5 and
- adds a field to the output indicating the architecture
compatibility.
libselinux can cope with an architecture mismatch by
ignoring the precompiled data in the input file and recompiling
the regular expressions at runtime. It can also load older
versions of file_contexts.bin if they where built with
sefcontext_compile using the exact same version of the
pcre1/2 as selinux.
Signed-off-by: Janis Danisevskis <jdanis@android.com>
This patch moves all pcre1/2 dependencies into the new files regex.h
and regex.c implementing the common denominator of features needed
by libselinux. The compiler flag -DUSE_PCRE2 toggles between the
used implementations.
As of this patch libselinux supports either pcre or pcre2 but not
both at the same time. The persistently stored file contexts
information differs. This means libselinux can only load file
context files generated by sefcontext_compile build with the
same pcre variant.
Also, for pcre2 the persistent format is architecture dependent.
Stored precompiled regular expressions can only be used on the
same architecture they were generated on. If pcre2 is used,
sefcontext_compile now respects the "-r". This flag makes
sefcontext_compile include the precompiled regular expressions
in the output file. The default is to omit them, so that the
output remains portable at the cost of having to recompile
the regular expressions at load time, or rather on first use.
Signed-off-by: Janis Danisevskis <jdanis@google.com>
