Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
module: Factor out elf_validity_cache_index_mod
Centralize .gnu.linkonce.this_module detection and property validation.
Signed-off-by: Matthew Maurer <mmaurer@google.com>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
authored by
Matthew Maurer
and committed by
Luis Chamberlain
0be41a93
fbc0e4e4
+67
-62
+67
-62
kernel/module/main.c
+67
-62
kernel/module/main.c
···
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return 0;
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}
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+
/**
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* elf_validity_cache_index_mod() - Validates and caches this_module section
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* @info: Load info to cache this_module on.
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* Must have &load_info->sechdrs and &load_info->secstrings populated
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*
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* The ".gnu.linkonce.this_module" ELF section is special. It is what modpost
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* uses to refer to __this_module and let's use rely on THIS_MODULE to point
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* to &__this_module properly. The kernel's modpost declares it on each
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* modules's *.mod.c file. If the struct module of the kernel changes a full
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* kernel rebuild is required.
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*
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* We have a few expectations for this special section, this function
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* validates all this for us:
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*
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* * The section has contents
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* * The section is unique
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* * We expect the kernel to always have to allocate it: SHF_ALLOC
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* * The section size must match the kernel's run time's struct module
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* size
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*
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* If all checks pass, the index will be cached in &load_info->index.mod
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*
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* Return: %0 on validation success, %-ENOEXEC on failure
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*/
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static int elf_validity_cache_index_mod(struct load_info *info)
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{
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Elf_Shdr *shdr;
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int mod_idx;
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+
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mod_idx = find_any_unique_sec(info, ".gnu.linkonce.this_module");
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if (mod_idx <= 0) {
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pr_err("module %s: Exactly one .gnu.linkonce.this_module section must exist.\n",
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info->name ?: "(missing .modinfo section or name field)");
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return -ENOEXEC;
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}
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+
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shdr = &info->sechdrs[mod_idx];
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+
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if (shdr->sh_type == SHT_NOBITS) {
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pr_err("module %s: .gnu.linkonce.this_module section must have a size set\n",
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info->name ?: "(missing .modinfo section or name field)");
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return -ENOEXEC;
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}
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+
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if (!(shdr->sh_flags & SHF_ALLOC)) {
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pr_err("module %s: .gnu.linkonce.this_module must occupy memory during process execution\n",
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info->name ?: "(missing .modinfo section or name field)");
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return -ENOEXEC;
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}
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+
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if (shdr->sh_size != sizeof(struct module)) {
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pr_err("module %s: .gnu.linkonce.this_module section size must match the kernel's built struct module size at run time\n",
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info->name ?: "(missing .modinfo section or name field)");
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return -ENOEXEC;
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}
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+
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info->index.mod = mod_idx;
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+
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return 0;
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}
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+
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+
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/*
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* Check userspace passed ELF module against our expectations, and cache
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* useful variables for further processing as we go.
···
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unsigned int i;
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Elf_Shdr *shdr;
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int err;
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-
unsigned int num_mod_secs = 0, mod_idx;
2010
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unsigned int num_sym_secs = 0, sym_idx;
2011
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2012
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err = elf_validity_cache_sechdrs(info);
···
2017
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err = elf_validity_cache_index_info(info);
2018
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if (err < 0)
2019
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return err;
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err = elf_validity_cache_index_mod(info);
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if (err < 0)
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return err;
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for (i = 1; i < info->hdr->e_shnum; i++) {
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shdr = &info->sechdrs[i];
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switch (shdr->sh_type) {
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case SHT_NULL:
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case SHT_NOBITS:
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continue;
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case SHT_SYMTAB:
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if (shdr->sh_type == SHT_SYMTAB) {
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if (shdr->sh_link == SHN_UNDEF
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|| shdr->sh_link >= info->hdr->e_shnum) {
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pr_err("Invalid ELF sh_link!=SHN_UNDEF(%d) or (sh_link(%d) >= hdr->e_shnum(%d)\n",
···
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}
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num_sym_secs++;
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sym_idx = i;
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fallthrough;
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default:
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if (strcmp(info->secstrings + shdr->sh_name,
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".gnu.linkonce.this_module") == 0) {
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num_mod_secs++;
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mod_idx = i;
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}
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break;
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}
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}
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···
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info->index.str = shdr->sh_link;
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info->strtab = (char *)info->hdr + info->sechdrs[info->index.str].sh_offset;
2050
1998
2051
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/*
2052
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* The ".gnu.linkonce.this_module" ELF section is special. It is
2053
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* what modpost uses to refer to __this_module and let's use rely
2054
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* on THIS_MODULE to point to &__this_module properly. The kernel's
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* modpost declares it on each modules's *.mod.c file. If the struct
2056
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* module of the kernel changes a full kernel rebuild is required.
2057
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*
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* We have a few expectaions for this special section, the following
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* code validates all this for us:
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*
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* o Only one section must exist
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* o We expect the kernel to always have to allocate it: SHF_ALLOC
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* o The section size must match the kernel's run time's struct module
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* size
2065
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*/
2066
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if (num_mod_secs != 1) {
2067
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pr_err("module %s: Only one .gnu.linkonce.this_module section must exist.\n",
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info->name ?: "(missing .modinfo section or name field)");
2069
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goto no_exec;
2070
-
}
2071
-
2072
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shdr = &info->sechdrs[mod_idx];
2073
-
2074
-
/*
2075
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* This is already implied on the switch above, however let's be
2076
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* pedantic about it.
2077
-
*/
2078
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if (shdr->sh_type == SHT_NOBITS) {
2079
-
pr_err("module %s: .gnu.linkonce.this_module section must have a size set\n",
2080
-
info->name ?: "(missing .modinfo section or name field)");
2081
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goto no_exec;
2082
-
}
2083
-
2084
-
if (!(shdr->sh_flags & SHF_ALLOC)) {
2085
-
pr_err("module %s: .gnu.linkonce.this_module must occupy memory during process execution\n",
2086
-
info->name ?: "(missing .modinfo section or name field)");
2087
-
goto no_exec;
2088
-
}
2089
-
2090
-
if (shdr->sh_size != sizeof(struct module)) {
2091
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pr_err("module %s: .gnu.linkonce.this_module section size must match the kernel's built struct module size at run time\n",
2092
-
info->name ?: "(missing .modinfo section or name field)");
2093
-
goto no_exec;
2094
-
}
2095
-
2096
-
info->index.mod = mod_idx;
2097
-
2098
1999
/* This is temporary: point mod into copy of data. */
2099
-
info->mod = (void *)info->hdr + shdr->sh_offset;
2000
+
info->mod = (void *)info->hdr + info->sechdrs[info->index.mod].sh_offset;
2100
2001
2101
2002
/*
2102
2003
* If we didn't load the .modinfo 'name' field earlier, fall back to