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modutils: support finit_module syscall

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On some systems like Chromium OS, loading modules from non-verified
filesystems is denied.  Only finit_module is allowed because an open
fd is passed which can be checked against a verified location.

Change the module loading code to first attempt finit_module and if
that fails for whatever reason, fall back to the existing logic.

On x86_64, this adds ~80 bytes to modutils/modutils.o and ~68 bytes
to modutils/modprobe-small.o.

Signed-off-by: Mike Frysinger <vapier@chromium.org>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Mike Frysinger
2016-09-15 12:16:33 +02:00
committed by Denys Vlasenko
parent 7fa799a97d
commit 3a45b87ac3
2 changed files with 51 additions and 3 deletions
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21
modutils/modutils.c
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@ -13,6 +13,9 @@ extern int delete_module(const char *module, unsigned int flags);
#else
# include <sys/syscall.h>
# define init_module(mod, len, opts) syscall(__NR_init_module, mod, len, opts)
# if defined(__NR_finit_module)
# define finit_module(fd, uargs, flags) syscall(__NR_finit_module, fd, uargs, flags)
# endif
# define delete_module(mod, flags) syscall(__NR_delete_module, mod, flags)
#endif
@ -212,6 +215,24 @@ int FAST_FUNC bb_init_module(const char *filename, const char *options)
return bb_init_module_24(filename, options);
#endif
/*
* First we try finit_module if available. Some kernels are configured
* to only allow loading of modules off of secure storage (like a read-
* only rootfs) which needs the finit_module call. If it fails, we fall
* back to normal module loading to support compressed modules.
*/
# ifdef __NR_finit_module
{
int fd = open(filename, O_RDONLY | O_CLOEXEC);
if (fd >= 0) {
rc = finit_module(fd, options, 0) != 0;
close(fd);
if (rc == 0)
return rc;
}
}
# endif
image_size = INT_MAX - 4095;
mmaped = 0;
image = try_to_mmap_module(filename, &image_size);