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module/retpoline: Warn about missing retpoline in module

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There's a risk that a kernel which has full retpoline mitigations becomes
vulnerable when a module gets loaded that hasn't been compiled with the
right compiler or the right option.

To enable detection of that mismatch at module load time, add a module info
string "retpoline" at build time when the module was compiled with
retpoline support. This only covers compiled C source, but assembler source
or prebuilt object files are not checked.

If a retpoline enabled kernel detects a non retpoline protected module at
load time, print a warning and report it in the sysfs vulnerability file.

[ tglx: Massaged changelog ]

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: gregkh@linuxfoundation.org
Cc: torvalds@linux-foundation.org
Cc: jeyu@kernel.org
Cc: arjan@linux.intel.com
Link: https://lkml.kernel.org/r/20180125235028.31211-1-andi@firstfloor.org
This commit is contained in:
Andi Kleen
2018-01-25 15:50:28 -08:00
committed by Thomas Gleixner
parent c940a3fb1e
commit caf7501a1b
4 changed files with 45 additions and 1 deletions
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9
scripts/mod/modpost.c
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@@ -2165,6 +2165,14 @@ static void add_intree_flag(struct buffer *b, int is_intree)
buf_printf(b, "\nMODULE_INFO(intree, \"Y\");\n");
}
/* Cannot check for assembler */
static void add_retpoline(struct buffer *b)
{
buf_printf(b, "\n#ifdef RETPOLINE\n");
buf_printf(b, "MODULE_INFO(retpoline, \"Y\");\n");
buf_printf(b, "#endif\n");
}
static void add_staging_flag(struct buffer *b, const char *name)
{
static const char *staging_dir = "drivers/staging";
@@ -2506,6 +2514,7 @@ int main(int argc, char **argv)
err |= check_modname_len(mod);
add_header(&buf, mod);
add_intree_flag(&buf, !external_module);
add_retpoline(&buf);
add_staging_flag(&buf, mod->name);
err |= add_versions(&buf, mod);
add_depends(&buf, mod, modules);