modpost: fix removing numeric suffixes
authorAlexander Lobakin <alexandr.lobakin@intel.com>
Tue, 24 May 2022 15:27:18 +0000 (17:27 +0200)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Tue, 14 Jun 2022 16:36:10 +0000 (18:36 +0200)
commita53131a69515dc170707df1ac17f3c4444169b87
tree50053accc529e7008a4077722bd43a6d6f24fa8e
parentc1df9cb756e5a9ba1841648c44ee5d92306b9c65
modpost: fix removing numeric suffixes

[ Upstream commit b5beffa20d83c4e15306c991ffd00de0d8628338 ]

With the `-z unique-symbol` linker flag or any similar mechanism,
it is possible to trigger the following:

ERROR: modpost: "param_set_uint.0" [vmlinux] is a static EXPORT_SYMBOL

The reason is that for now the condition from remove_dot():

if (m && (s[n + m] == '.' || s[n + m] == 0))

which was designed to test if it's a dot or a '\0' after the suffix
is never satisfied.
This is due to that `s[n + m]` always points to the last digit of a
numeric suffix, not on the symbol next to it (from a custom debug
print added to modpost):

param_set_uint.0, s[n + m] is '0', s[n + m + 1] is '\0'

So it's off-by-one and was like that since 2014.

Fix this for the sake of any potential upcoming features, but don't
bother stable-backporting, as it's well hidden -- apart from that
LD flag, it can be triggered only with GCC LTO which never landed
upstream.

Fixes: fcd38ed0ff26 ("scripts: modpost: fix compilation warning")
Signed-off-by: Alexander Lobakin <alexandr.lobakin@intel.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
scripts/mod/modpost.c