On 2/7/19 12:52 PM, Roberts, William C wrote:
-----Original Message-----
From: Petr Lautrbach [mailto:plautrba@xxxxxxxxxx]
Sent: Thursday, February 7, 2019 4:40 AM
To: selinux@xxxxxxxxxxxxxxx
Cc: Petr Lautrbach <plautrba@xxxxxxxxxx>; Roberts, William C
<william.c.roberts@xxxxxxxxx>; Ondrej Mosnacek <omosnace@xxxxxxxxxx>
Subject: Re: gcc 9.0.0 build issues
Ondrej Mosnacek <omosnace@xxxxxxxxxx> writes:
On Fri, Feb 1, 2019 at 8:36 PM Petr Lautrbach <plautrba@xxxxxxxxxx>
wrote:
gcc-9.0.0-0.3.fc30.x86_64 from Fedora Rawhide:
gcc version 9.0.0 20190119 (Red Hat 9.0.0-0.3) (GCC)
...
When libselinux is built separately, other CFLAGS is used:
$ cd libselinux
$ make DESTDIR=~/obj install install-pywrap ...
make[1]: Entering directory
'/home/build/SELinuxProject-selinux/libselinux/src'
cc -O -Wall -W -Wundef -Wformat-y2k -Wformat-security -Winit-self
-Wmissing-include-dirs -Wunused -Wunknown-pragmas -Wstrict-aliasing
-Wshadow -Wpointer-arith -Wbad-function-cast -Wcast-align
-Wwrite-strings -Waggregate-return -Wstrict-prototypes
-Wold-style-definition -Wmissing-prototypes -Wmissing-declarations
-Wmissing-noreturn -Wmissing-format-attribute -Wredundant-decls
-Wnested-externs -Winline -Winvalid-pch -Wvolatile-register-var
-Wdisabled-optimization -Wbuiltin-macro-redefined -Wattributes
-Wmultichar -Wdeprecated-declarations -Wdiv-by-zero
-Wdouble-promotion -Wendif-labels -Wextra -Wformat-extra-args
-Wformat-zero-length -Wformat=2 -Wmultichar -Woverflow
-Wpointer-to-int-cast -Wpragmas -Wno-missing-field-initializers
-Wno-sign-compare -Wno-format-nonliteral
-Wframe-larger-than=32768
-fstack-protector-all --param=ssp-buffer-size=4 -fexceptions
-fasynchronous-unwind-tables -fdiagnostics-show-option
-funit-at-a-time -Werror -Wno-aggregate-return -Wno-redundant-decls
-fipa-pure-const -Wlogical-op -Wpacked-bitfield-compat -Wsync-nand
-Wcoverage-mismatch -Wcpp -Wformat-contains-nul -Wnormalized=nfc
-Wsuggest-attribute=const -Wsuggest-attribute=noreturn
-Wsuggest-attribute=pure -Wtrampolines -Wjump-misses-init
-Wno-suggest-attribute=pure -Wno-suggest-attribute=const
-U_FORTIFY_SOURCE
-D_FORTIFY_SOURCE=2
-Wstrict-overflow=5 -I../include -D_GNU_SOURCE
-DNO_ANDROID_BACKEND -c -o booleans.o booleans.c
booleans.c: In function ‘security_get_boolean_names’:
booleans.c:39:5: error: assuming signed overflow does not occur when
changing X +- C1 cmp C2 to X cmp C2 -+ C1 [-Werror=strict-overflow]
39 | int security_get_boolean_names(char ***names, int *len)
| ^~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
This one is really weird... Perhaps a bug in GCC? At the very least
the warning message and source code location are super confusing,
which is a bug on its own...
It's detected only with -Wstrict-overflow=3 and higher. Makefile in libselinux uses
level 5 which was added by commit
9fe430345 ("Makefile: add -Wstrict-overflow=5 to CFLAGS)
The problem code is on lines 84 and 85 in
libselinux/src/booleans.c:
84: for (--i; i >= 0; --i)
85: free(n[i]);
It could be suppressed by something like this:
--- a/libselinux/src/booleans.c
+++ b/libselinux/src/booleans.c
@@ -39,7 +39,7 @@ static int filename_select(const struct dirent
*d)
int security_get_boolean_names(char ***names, int *len) {
char path[PATH_MAX];
- int i, rc;
+ int i, j, rc;
struct dirent **namelist;
char **n;
@@ -81,8 +81,8 @@ int security_get_boolean_names(char ***names, int *len)
free(namelist);
return rc;
bad_freen:
- for (--i; i >= 0; --i)
- free(n[i]);
+ for (j = 0; j < i; j++)
+ free(n[j]);
free(n);
bad:
goto out;
William, what would you consider to be the right fix in this case?
The previous code looks correct IMO, I can't see an actual problem. Looks like
GCC complaining incorrectly or were missing something. In the case of gcc
Incorrectly complaining I usually take a course of action to work around it, but
Im not sure how other maintainers feel about that @sds anything?
AFAICS, the code is correct as is. Not a fan of rewriting code to
appease overly zealous compilers...
