Messages in this thread | | | From | Geert Uytterhoeven <> | Date | Mon, 25 Sep 2017 13:29:11 +0200 | Subject | Re: [PATCH] apparmor: initialized returned struct aa_perms |
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On Fri, Sep 15, 2017 at 9:55 PM, Arnd Bergmann <arnd@arndb.de> wrote: > gcc-4.4 points out suspicious code in compute_mnt_perms, where > the aa_perms structure is only partially initialized before getting > returned: > > security/apparmor/mount.c: In function 'compute_mnt_perms': > security/apparmor/mount.c:227: error: 'perms.prompt' is used uninitialized in this function > security/apparmor/mount.c:227: error: 'perms.hide' is used uninitialized in this function > security/apparmor/mount.c:227: error: 'perms.cond' is used uninitialized in this function > security/apparmor/mount.c:227: error: 'perms.complain' is used uninitialized in this function > security/apparmor/mount.c:227: error: 'perms.stop' is used uninitialized in this function > security/apparmor/mount.c:227: error: 'perms.deny' is used uninitialized in this function > > Returning or assigning partially initialized structures is a bit tricky, > in particular it is explicitly allowed in c99 to assign a partially > intialized structure to another, as long as only members are read that > have been initialized earlier. Looking at what various compilers do here, > the version that produced the warning copied unintialized stack data, > while newer versions (and also clang) either set the other members to > zero or don't update the parts of the return buffer that are not modified > in the temporary structure, but they never warn about this. > > In case of apparmor, it seems better to be a little safer and always > initialize the aa_perms structure. Most users already do that, this > changes the remaining ones, including the one instance that I got the > warning for. > > Fixes: fa488437d0f9 ("apparmor: add mount mediation") > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
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