| Message ID | 20220209185752.1226407-2-alexandr.lobakin@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Function Granular KASLR | expand |
On Thu, Feb 10, 2022 at 3:59 AM Alexander Lobakin <alexandr.lobakin@intel.com> wrote: > > `-z unique-symbol` linker flag which is planned to use with FG-KASLR > to simplify livepatching (hopefully globally later on) triggers 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 upcoming features, but don't bother > stable-backporting, as it's well hidden -- apart from that LD flag, > can be triggered only by GCC LTO which never landed upstream. > > Fixes: fcd38ed0ff26 ("scripts: modpost: fix compilation warning") > Signed-off-by: Alexander Lobakin <alexandr.lobakin@intel.com> > --- Acked-by: Masahiro Yamada <masahiroy@kernel.org> > scripts/mod/modpost.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c > index 6bfa33217914..4648b7afe5cc 100644 > --- a/scripts/mod/modpost.c > +++ b/scripts/mod/modpost.c > @@ -1986,7 +1986,7 @@ static char *remove_dot(char *s) > > if (n && s[n]) { > size_t m = strspn(s + n + 1, "0123456789"); > - if (m && (s[n + m] == '.' || s[n + m] == 0)) > + if (m && (s[n + m + 1] == '.' || s[n + m + 1] == 0)) > s[n] = 0; > > /* strip trailing .lto */ > -- > 2.34.1 >
On Wed 2022-02-09 19:57:38, Alexander Lobakin wrote: > `-z unique-symbol` linker flag which is planned to use with FG-KASLR > to simplify livepatching (hopefully globally later on) triggers 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' Yup, the + 1 is for the '.' between the symbol name and the number. In the order of apperance it would be: n + 1 + m > So it's off-by-one and was like that since 2014. > Fix this for the sake of upcoming features, but don't bother > stable-backporting, as it's well hidden -- apart from that LD flag, > can be triggered only by 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> Best Regards, Petr
On Thu, Feb 10, 2022 at 3:59 AM Alexander Lobakin <alexandr.lobakin@intel.com> wrote: > > `-z unique-symbol` linker flag which is planned to use with FG-KASLR > to simplify livepatching (hopefully globally later on) triggers 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 upcoming features, but don't bother > stable-backporting, as it's well hidden -- apart from that LD flag, > can be triggered only by GCC LTO which never landed upstream. > > Fixes: fcd38ed0ff26 ("scripts: modpost: fix compilation warning") > Signed-off-by: Alexander Lobakin <alexandr.lobakin@intel.com> > --- > scripts/mod/modpost.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c > index 6bfa33217914..4648b7afe5cc 100644 > --- a/scripts/mod/modpost.c > +++ b/scripts/mod/modpost.c > @@ -1986,7 +1986,7 @@ static char *remove_dot(char *s) > > if (n && s[n]) { > size_t m = strspn(s + n + 1, "0123456789"); > - if (m && (s[n + m] == '.' || s[n + m] == 0)) > + if (m && (s[n + m + 1] == '.' || s[n + m + 1] == 0)) > s[n] = 0; > > /* strip trailing .lto */ > -- > 2.34.1 > This trivial patch has not been picked up yet. I can apply this to my tree, if you want. Please let me know your thoughts.
From: Masahiro Yamada <masahiroy@kernel.org> Date: Tue, 24 May 2022 03:04:00 +0900 > On Thu, Feb 10, 2022 at 3:59 AM Alexander Lobakin > <alexandr.lobakin@intel.com> wrote: > > > > `-z unique-symbol` linker flag which is planned to use with FG-KASLR > > to simplify livepatching (hopefully globally later on) triggers 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 upcoming features, but don't bother > > stable-backporting, as it's well hidden -- apart from that LD flag, > > can be triggered only by GCC LTO which never landed upstream. > > > > Fixes: fcd38ed0ff26 ("scripts: modpost: fix compilation warning") > > Signed-off-by: Alexander Lobakin <alexandr.lobakin@intel.com> > > --- > > scripts/mod/modpost.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c > > index 6bfa33217914..4648b7afe5cc 100644 > > --- a/scripts/mod/modpost.c > > +++ b/scripts/mod/modpost.c > > @@ -1986,7 +1986,7 @@ static char *remove_dot(char *s) > > > > if (n && s[n]) { > > size_t m = strspn(s + n + 1, "0123456789"); > > - if (m && (s[n + m] == '.' || s[n + m] == 0)) > > + if (m && (s[n + m + 1] == '.' || s[n + m + 1] == 0)) > > s[n] = 0; > > > > /* strip trailing .lto */ > > -- > > 2.34.1 > > > > This trivial patch has not been picked up yet. > > I can apply this to my tree, if you want. It's a good idea, I'd like to! I don't use `-z unique-symbol` for FG-KALSR anymore*, but this fix is not directly related to it and can be taken independently. Should I change the commit message or it's ok to take it as it is? > > Please let me know your thoughts. > > > -- > Best Regards > Masahiro Yamada * I'm planning to submit a new rev of FG-KASLR series soon, but since I'm too busy with XDP for now, it will happen no sooner than in a couple months =\ Thanks! Al
On Tue, May 24, 2022 at 8:34 PM Alexander Lobakin <alexandr.lobakin@intel.com> wrote: > > From: Masahiro Yamada <masahiroy@kernel.org> > Date: Tue, 24 May 2022 03:04:00 +0900 > > > On Thu, Feb 10, 2022 at 3:59 AM Alexander Lobakin > > <alexandr.lobakin@intel.com> wrote: > > > > > > `-z unique-symbol` linker flag which is planned to use with FG-KASLR > > > to simplify livepatching (hopefully globally later on) triggers 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 upcoming features, but don't bother > > > stable-backporting, as it's well hidden -- apart from that LD flag, > > > can be triggered only by GCC LTO which never landed upstream. > > > > > > Fixes: fcd38ed0ff26 ("scripts: modpost: fix compilation warning") > > > Signed-off-by: Alexander Lobakin <alexandr.lobakin@intel.com> > > > --- > > > scripts/mod/modpost.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c > > > index 6bfa33217914..4648b7afe5cc 100644 > > > --- a/scripts/mod/modpost.c > > > +++ b/scripts/mod/modpost.c > > > @@ -1986,7 +1986,7 @@ static char *remove_dot(char *s) > > > > > > if (n && s[n]) { > > > size_t m = strspn(s + n + 1, "0123456789"); > > > - if (m && (s[n + m] == '.' || s[n + m] == 0)) > > > + if (m && (s[n + m + 1] == '.' || s[n + m + 1] == 0)) > > > s[n] = 0; > > > > > > /* strip trailing .lto */ > > > -- > > > 2.34.1 > > > > > > > This trivial patch has not been picked up yet. > > > > I can apply this to my tree, if you want. > > It's a good idea, I'd like to! > I don't use `-z unique-symbol` for FG-KALSR anymore*, but this fix > is not directly related to it and can be taken independently. > Should I change the commit message or it's ok to take it as it is? I am fine with either way. If you want to resubmit this with a fresh commit log, please send it to: linux-kbuild@vger.kernel.org Then, I will take care of it in this MW. Thanks. > > > > Please let me know your thoughts. > > > > > > -- > > Best Regards > > Masahiro Yamada > > * I'm planning to submit a new rev of FG-KASLR series soon, but > since I'm too busy with XDP for now, it will happen no sooner than > in a couple months =\ > > Thanks! > Al
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c index 6bfa33217914..4648b7afe5cc 100644 --- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -1986,7 +1986,7 @@ static char *remove_dot(char *s) if (n && s[n]) { size_t m = strspn(s + n + 1, "0123456789"); - if (m && (s[n + m] == '.' || s[n + m] == 0)) + if (m && (s[n + m + 1] == '.' || s[n + m + 1] == 0)) s[n] = 0; /* strip trailing .lto */
`-z unique-symbol` linker flag which is planned to use with FG-KASLR to simplify livepatching (hopefully globally later on) triggers 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 upcoming features, but don't bother stable-backporting, as it's well hidden -- apart from that LD flag, can be triggered only by GCC LTO which never landed upstream. Fixes: fcd38ed0ff26 ("scripts: modpost: fix compilation warning") Signed-off-by: Alexander Lobakin <alexandr.lobakin@intel.com> --- scripts/mod/modpost.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)