Messages in this thread | | | Date | Wed, 29 Jun 2011 18:42:43 +0200 | Subject | Re: [PATCH 1/4] um: Fix _FORTIFY_SOURCE=2 support for kernel modules | From | Geert Uytterhoeven <> |
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On Wed, Jun 29, 2011 at 17:42, Richard Weinberger <richard@nod.at> wrote: > Am Mittwoch 29 Juni 2011, 17:37:54 schrieb Vitaliy Ivanov: >> On Tue, Jun 28, 2011 at 1:15 AM, Richard Weinberger <richard@nod.at> wrote: >> > When UML is compiled with _FORTIFY_SOURCE we have to >> > export all _chk() functions which are used in modules. >> > For now it's only the case for __sprintf_chk(). >> > >> > Tested-by: Florian Fainelli <florian@openwrt.org> >> > Reported-by: Florian Fainelli <florian@openwrt.org> >> > Signed-off-by: Richard Weinberger <richard@nod.at> >> > --- >> > arch/um/os-Linux/user_syms.c | 5 +++++ >> > 1 files changed, 5 insertions(+), 0 deletions(-) >> > >> > diff --git a/arch/um/os-Linux/user_syms.c b/arch/um/os-Linux/user_syms.c >> > index 05f5ea8..45ffe46 100644 >> > --- a/arch/um/os-Linux/user_syms.c >> > +++ b/arch/um/os-Linux/user_syms.c >> > @@ -113,3 +113,8 @@ EXPORT_SYMBOL(__stack_smash_handler); >> > >> > extern long __guard __attribute__((weak)); >> > EXPORT_SYMBOL(__guard); >> > + >> > +#ifdef _FORTIFY_SOURCE >> > +extern int __sprintf_chk(char *str, int flag, size_t strlen, const char >> > *format); +EXPORT_SYMBOL(__sprintf_chk); >> > +#endif >> > -- >> >> Can you please clarify why it's needed? I use FORTIFY_SOURCES on >> Linus' tree UML on Ubuntu w/ no problems and w/o this patch... > > The problem appears only when a UML kernel module is using sprintf(). > E.g: CONFIG_UML_WATCHDOG. > Then loading the module will fail because of the missing symbol __sprintf_chk().
What about changing harddog_user.c to not use sprintf(), but snprintf()?
Besides, the code does look fishy to me:
char pid_buf[sizeof("nnnnn\0")]; sprintf(pid_buf, "%d", os_getpid());
os_getpid() returns int:
int os_getpid(void) { return syscall(__NR_getpid); }
but sys_getpid() returns long.
So we truncate a (possibly 64-bit number) to 32-bit, and format it in a buffer that has space for 5 chars only...
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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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