| Message ID | 20230613004125.3539934-1-azeemshaikh38@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Commit | 38638ffa6059049334b4d87bd4d85cf3418b5e27 |
| Headers | show |
| Series | tracing/boot: Replace strlcpy with strscpy | expand |
On Tue, Jun 13, 2023 at 12:41:25AM +0000, Azeem Shaikh wrote: > strlcpy() reads the entire source buffer first. > This read may exceed the destination size limit. > This is both inefficient and can lead to linear read > overflows if a source string is not NUL-terminated [1]. > In an effort to remove strlcpy() completely [2], replace > strlcpy() here with strscpy(). > > Direct replacement is safe here since return value of -E2BIG > is used to check for truncation instead of sizeof(dest). This looks technically correct, but I wonder if "< 0" is a better test? > > [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy > [2] https://github.com/KSPP/linux/issues/89 > > Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com> Either way Reviewed-by: Kees Cook <keescook@chromium.org> -Kees > --- > kernel/trace/trace_boot.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/kernel/trace/trace_boot.c b/kernel/trace/trace_boot.c > index 778200dd8ede..5fe525f1b8cc 100644 > --- a/kernel/trace/trace_boot.c > +++ b/kernel/trace/trace_boot.c > @@ -31,7 +31,7 @@ trace_boot_set_instance_options(struct trace_array *tr, struct xbc_node *node) > > /* Common ftrace options */ > xbc_node_for_each_array_value(node, "options", anode, p) { > - if (strlcpy(buf, p, ARRAY_SIZE(buf)) >= ARRAY_SIZE(buf)) { > + if (strscpy(buf, p, ARRAY_SIZE(buf)) == -E2BIG) { > pr_err("String is too long: %s\n", p); > continue; > } > @@ -87,7 +87,7 @@ trace_boot_enable_events(struct trace_array *tr, struct xbc_node *node) > const char *p; > > xbc_node_for_each_array_value(node, "events", anode, p) { > - if (strlcpy(buf, p, ARRAY_SIZE(buf)) >= ARRAY_SIZE(buf)) { > + if (strscpy(buf, p, ARRAY_SIZE(buf)) == -E2BIG) { > pr_err("String is too long: %s\n", p); > continue; > } > @@ -486,7 +486,7 @@ trace_boot_init_one_event(struct trace_array *tr, struct xbc_node *gnode, > > p = xbc_node_find_value(enode, "filter", NULL); > if (p && *p != '\0') { > - if (strlcpy(buf, p, ARRAY_SIZE(buf)) >= ARRAY_SIZE(buf)) > + if (strscpy(buf, p, ARRAY_SIZE(buf)) == -E2BIG) > pr_err("filter string is too long: %s\n", p); > else if (apply_event_filter(file, buf) < 0) > pr_err("Failed to apply filter: %s\n", buf); > @@ -494,7 +494,7 @@ trace_boot_init_one_event(struct trace_array *tr, struct xbc_node *gnode, > > if (IS_ENABLED(CONFIG_HIST_TRIGGERS)) { > xbc_node_for_each_array_value(enode, "actions", anode, p) { > - if (strlcpy(buf, p, ARRAY_SIZE(buf)) >= ARRAY_SIZE(buf)) > + if (strscpy(buf, p, ARRAY_SIZE(buf)) == -E2BIG) > pr_err("action string is too long: %s\n", p); > else if (trigger_process_regex(file, buf) < 0) > pr_err("Failed to apply an action: %s\n", p); > -- > 2.41.0.162.gfafddb0af9-goog > >
On Tue, Jun 13, 2023 at 3:27 PM Kees Cook <keescook@chromium.org> wrote: > > On Tue, Jun 13, 2023 at 12:41:25AM +0000, Azeem Shaikh wrote: > > strlcpy() reads the entire source buffer first. > > This read may exceed the destination size limit. > > This is both inefficient and can lead to linear read > > overflows if a source string is not NUL-terminated [1]. > > In an effort to remove strlcpy() completely [2], replace > > strlcpy() here with strscpy(). > > > > Direct replacement is safe here since return value of -E2BIG > > is used to check for truncation instead of sizeof(dest). > > This looks technically correct, but I wonder if "< 0" is a better test? Agreed. "< 0" might more generically represent -errno. Happy to send over a v2 if you prefer that instead of sticking with this patch. > > > > > [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy > > [2] https://github.com/KSPP/linux/issues/89 > > > > Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com> > > Either way > > Reviewed-by: Kees Cook <keescook@chromium.org> > > -Kees > > > --- > > kernel/trace/trace_boot.c | 8 ++++---- > > 1 file changed, 4 insertions(+), 4 deletions(-) > > > > diff --git a/kernel/trace/trace_boot.c b/kernel/trace/trace_boot.c > > index 778200dd8ede..5fe525f1b8cc 100644 > > --- a/kernel/trace/trace_boot.c > > +++ b/kernel/trace/trace_boot.c > > @@ -31,7 +31,7 @@ trace_boot_set_instance_options(struct trace_array *tr, struct xbc_node *node) > > > > /* Common ftrace options */ > > xbc_node_for_each_array_value(node, "options", anode, p) { > > - if (strlcpy(buf, p, ARRAY_SIZE(buf)) >= ARRAY_SIZE(buf)) { > > + if (strscpy(buf, p, ARRAY_SIZE(buf)) == -E2BIG) { > > pr_err("String is too long: %s\n", p); > > continue; > > } > > @@ -87,7 +87,7 @@ trace_boot_enable_events(struct trace_array *tr, struct xbc_node *node) > > const char *p; > > > > xbc_node_for_each_array_value(node, "events", anode, p) { > > - if (strlcpy(buf, p, ARRAY_SIZE(buf)) >= ARRAY_SIZE(buf)) { > > + if (strscpy(buf, p, ARRAY_SIZE(buf)) == -E2BIG) { > > pr_err("String is too long: %s\n", p); > > continue; > > } > > @@ -486,7 +486,7 @@ trace_boot_init_one_event(struct trace_array *tr, struct xbc_node *gnode, > > > > p = xbc_node_find_value(enode, "filter", NULL); > > if (p && *p != '\0') { > > - if (strlcpy(buf, p, ARRAY_SIZE(buf)) >= ARRAY_SIZE(buf)) > > + if (strscpy(buf, p, ARRAY_SIZE(buf)) == -E2BIG) > > pr_err("filter string is too long: %s\n", p); > > else if (apply_event_filter(file, buf) < 0) > > pr_err("Failed to apply filter: %s\n", buf); > > @@ -494,7 +494,7 @@ trace_boot_init_one_event(struct trace_array *tr, struct xbc_node *gnode, > > > > if (IS_ENABLED(CONFIG_HIST_TRIGGERS)) { > > xbc_node_for_each_array_value(enode, "actions", anode, p) { > > - if (strlcpy(buf, p, ARRAY_SIZE(buf)) >= ARRAY_SIZE(buf)) > > + if (strscpy(buf, p, ARRAY_SIZE(buf)) == -E2BIG) > > pr_err("action string is too long: %s\n", p); > > else if (trigger_process_regex(file, buf) < 0) > > pr_err("Failed to apply an action: %s\n", p); > > -- > > 2.41.0.162.gfafddb0af9-goog > > > > > > -- > Kees Cook
On Wed, Jun 14, 2023 at 10:01:57AM -0400, Azeem Shaikh wrote: > On Tue, Jun 13, 2023 at 3:27 PM Kees Cook <keescook@chromium.org> wrote: > > > > On Tue, Jun 13, 2023 at 12:41:25AM +0000, Azeem Shaikh wrote: > > > strlcpy() reads the entire source buffer first. > > > This read may exceed the destination size limit. > > > This is both inefficient and can lead to linear read > > > overflows if a source string is not NUL-terminated [1]. > > > In an effort to remove strlcpy() completely [2], replace > > > strlcpy() here with strscpy(). > > > > > > Direct replacement is safe here since return value of -E2BIG > > > is used to check for truncation instead of sizeof(dest). > > > > This looks technically correct, but I wonder if "< 0" is a better test? > > Agreed. "< 0" might more generically represent -errno. Happy to send > over a v2 if you prefer that instead of sticking with this patch. Please go with "< 0", since it's easier to read and less error-prone. (It would be easy to mistype -E2BIG as -EFBIG, or E2BIG, for example...) - Eric
On Wed, Jun 14, 2023 at 1:13 PM Eric Biggers <ebiggers@kernel.org> wrote: > > On Wed, Jun 14, 2023 at 10:01:57AM -0400, Azeem Shaikh wrote: > > On Tue, Jun 13, 2023 at 3:27 PM Kees Cook <keescook@chromium.org> wrote: > > > > > > On Tue, Jun 13, 2023 at 12:41:25AM +0000, Azeem Shaikh wrote: > > > > strlcpy() reads the entire source buffer first. > > > > This read may exceed the destination size limit. > > > > This is both inefficient and can lead to linear read > > > > overflows if a source string is not NUL-terminated [1]. > > > > In an effort to remove strlcpy() completely [2], replace > > > > strlcpy() here with strscpy(). > > > > > > > > Direct replacement is safe here since return value of -E2BIG > > > > is used to check for truncation instead of sizeof(dest). > > > > > > This looks technically correct, but I wonder if "< 0" is a better test? > > > > Agreed. "< 0" might more generically represent -errno. Happy to send > > over a v2 if you prefer that instead of sticking with this patch. > > Please go with "< 0", since it's easier to read and less error-prone. (It would > be easy to mistype -E2BIG as -EFBIG, or E2BIG, for example...) > Thanks, sent out a v2 with this change.
diff --git a/kernel/trace/trace_boot.c b/kernel/trace/trace_boot.c index 778200dd8ede..5fe525f1b8cc 100644 --- a/kernel/trace/trace_boot.c +++ b/kernel/trace/trace_boot.c @@ -31,7 +31,7 @@ trace_boot_set_instance_options(struct trace_array *tr, struct xbc_node *node) /* Common ftrace options */ xbc_node_for_each_array_value(node, "options", anode, p) { - if (strlcpy(buf, p, ARRAY_SIZE(buf)) >= ARRAY_SIZE(buf)) { + if (strscpy(buf, p, ARRAY_SIZE(buf)) == -E2BIG) { pr_err("String is too long: %s\n", p); continue; } @@ -87,7 +87,7 @@ trace_boot_enable_events(struct trace_array *tr, struct xbc_node *node) const char *p; xbc_node_for_each_array_value(node, "events", anode, p) { - if (strlcpy(buf, p, ARRAY_SIZE(buf)) >= ARRAY_SIZE(buf)) { + if (strscpy(buf, p, ARRAY_SIZE(buf)) == -E2BIG) { pr_err("String is too long: %s\n", p); continue; } @@ -486,7 +486,7 @@ trace_boot_init_one_event(struct trace_array *tr, struct xbc_node *gnode, p = xbc_node_find_value(enode, "filter", NULL); if (p && *p != '\0') { - if (strlcpy(buf, p, ARRAY_SIZE(buf)) >= ARRAY_SIZE(buf)) + if (strscpy(buf, p, ARRAY_SIZE(buf)) == -E2BIG) pr_err("filter string is too long: %s\n", p); else if (apply_event_filter(file, buf) < 0) pr_err("Failed to apply filter: %s\n", buf); @@ -494,7 +494,7 @@ trace_boot_init_one_event(struct trace_array *tr, struct xbc_node *gnode, if (IS_ENABLED(CONFIG_HIST_TRIGGERS)) { xbc_node_for_each_array_value(enode, "actions", anode, p) { - if (strlcpy(buf, p, ARRAY_SIZE(buf)) >= ARRAY_SIZE(buf)) + if (strscpy(buf, p, ARRAY_SIZE(buf)) == -E2BIG) pr_err("action string is too long: %s\n", p); else if (trigger_process_regex(file, buf) < 0) pr_err("Failed to apply an action: %s\n", p);
strlcpy() reads the entire source buffer first. This read may exceed the destination size limit. This is both inefficient and can lead to linear read overflows if a source string is not NUL-terminated [1]. In an effort to remove strlcpy() completely [2], replace strlcpy() here with strscpy(). Direct replacement is safe here since return value of -E2BIG is used to check for truncation instead of sizeof(dest). [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy [2] https://github.com/KSPP/linux/issues/89 Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com> --- kernel/trace/trace_boot.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)