module: merge remnants of setup_load_info() to elf validation

The setup_load_info() was actually had ELF validation checks of its own. To later cache useful variables as an secondary step just means looping again over the ELF sections we just validated. We can simply keep tabs of the key sections of interest as we validate the module ELF section in one swoop, so do that and merge the two routines together. Expand a bit on the documentation / intent / goals.

Luis Chamberlain committed 3 years ago

Commit 3d40bb91 parent 1bb49db1 file · +27 −33Browse files

Showing the changes to kernel/module (1 of 1 file). Show all

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kernel/module/main.c+27−33

@@ -1647,12 +1647,26 @@ static int validate_section_offset(struct load_info info, Elf_Shdr shdr) · 1646 unmodified lines
1647	1647	}
1648	1648
1649	1649	/*
1650		− * Sanity checks against invalid binaries, wrong arch, weird elf version.
	1650	+ * Check userspace passed ELF module against our expectations, and cache
	1651	+ * useful variables for further processing as we go.
1651	1652	*
1652		− * Also do basic validity checks against section offsets and sizes, the
	1653	+ * This does basic validity checks against section offsets and sizes, the
1653	1654	* section name string table, and the indices used for it (sh_name).
	1655	+ *
	1656	+ * As a last step, since we're already checking the ELF sections we cache
	1657	+ * useful variables which will be used later for our convenience:
	1658	+ *
	1659	+ * o pointers to section headers
	1660	+ * o cache the modinfo symbol section
	1661	+ * o cache the string symbol section
	1662	+ * o cache the module section
	1663	+ *
	1664	+ * As a last step we set info->mod to the temporary copy of the module in
	1665	+ * info->hdr. The final one will be allocated in move_module(). Any
	1666	+ * modifications we make to our copy of the module will be carried over
	1667	+ * to the final minted module.
1654	1668	*/
1655		−static int elf_validity_check(struct load_info *info)
	1669	+static int elf_validity_cache_copy(struct load_info *info, int flags)
1656	1670	{
1657	1671	unsigned int i;
1658	1672	Elf_Shdr shdr, strhdr;
@@ -1872,6 +1886,13 @@ static int elf_validity_check(struct load_info *info) · 213 unmodified lines
1872	1886	if (!info->name)
1873	1887	info->name = info->mod->name;
1874	1888
	1889	+ if (flags & MODULE_INIT_IGNORE_MODVERSIONS)
	1890	+ info->index.vers = 0; /* Pretend no __versions section! */
	1891	+ else
	1892	+ info->index.vers = find_sec(info, "__versions");
	1893	+
	1894	+ info->index.pcpu = find_pcpusec(info);
	1895	+
1875	1896	return 0;
1876	1897
1877	1898	no_exec:
@@ -1984,26 +2005,6 @@ static int rewrite_section_headers(struct load_info *info, int flags) · 106 unmodified lines
1984	2005	return 0;
1985	2006	}
1986	2007
1987		−/*
1988		− * Set up our basic convenience variables (pointers to section headers,
1989		− * search for module section index etc), and do some basic section
1990		− * verification.
1991		− *
1992		− * Set info->mod to the temporary copy of the module in info->hdr. The final one
1993		− * will be allocated in move_module().
1994		− */
1995		−static int setup_load_info(struct load_info *info, int flags)
1996		−{
1997		− if (flags & MODULE_INIT_IGNORE_MODVERSIONS)
1998		− info->index.vers = 0; /* Pretend no __versions section! */
1999		− else
2000		− info->index.vers = find_sec(info, "__versions");
2001		−
2002		− info->index.pcpu = find_pcpusec(info);
2003		−
2004		− return 0;
2005		−}
2006		−
2007	2008	/*
2008	2009	* These calls taint the kernel depending certain module circumstances */
2009	2010	static void module_augment_kernel_taints(struct module mod, struct load_info info)
@@ -2809,17 +2810,10 @@ static int load_module(struct load_info info, const char __user uargs, · 799 unmodified lines
2809	2810
2810	2811	/*
2811	2812	* Do basic sanity checks against the ELF header and
2812		− * sections.
2813		− */
2814		− err = elf_validity_check(info);
2815		− if (err)
2816		− goto free_copy;
2817		−
2818		− /*
2819		− * Everything checks out, so set up the section info
2820		− * in the info structure.
	2813	+ * sections. Cache useful sections and set the
	2814	+ * info->mod to the userspace passed struct module.
2821	2815	*/
2822		− err = setup_load_info(info, flags);
	2816	+ err = elf_validity_cache_copy(info, flags);
2823	2817	if (err)
2824	2818	goto free_copy;
2825	2819