From ab7e8bb6e077a55ae5ac1a4bb4ebba85470d47e5 Mon Sep 17 00:00:00 2001 From: Justin Stitt Date: Thu, 19 Oct 2023 17:54:15 +0000 Subject: [PATCH] nvdimm/btt: replace deprecated strncpy with strscpy Found with grep. strncpy() is deprecated for use on NUL-terminated destination strings [1] and as such we should prefer more robust and less ambiguous string interfaces. We expect super->signature to be NUL-terminated based on its usage with memcmp against a NUL-term'd buffer: btt_devs.c: 253 | if (memcmp(super->signature, BTT_SIG, BTT_SIG_LEN) != 0) btt.h: 13 | #define BTT_SIG "BTT_ARENA_INFO\0" NUL-padding is not required as `super` is already zero-allocated: btt.c: 985 | super = kzalloc(sizeof(struct btt_sb), GFP_NOIO); ... rendering any additional NUL-padding superfluous. Considering the above, a suitable replacement is `strscpy` [2] due to the fact that it guarantees NUL-termination on the destination buffer without unnecessarily NUL-padding. Let's also use the more idiomatic strscpy usage of (dest, src, sizeof(dest)) instead of (dest, src, XYZ_LEN) for buffers that the compiler can determine the size of. This more tightly correlates the destination buffer to the amount of bytes copied. Side note, this pattern of memcmp() on two NUL-terminated strings should really be changed to just a strncmp(), if i'm not mistaken? I see multiple instances of this pattern in this system: | if (memcmp(super->signature, BTT_SIG, BTT_SIG_LEN) != 0) | return false; where BIT_SIG is defined (weirdly) as a double NUL-terminated string: | #define BTT_SIG "BTT_ARENA_INFO\0" Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1] Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2] Link: https://github.com/KSPP/linux/issues/90 Cc: linux-hardening@vger.kernel.org Signed-off-by: Justin Stitt Reviewed-by: Kees Cook Link: https://lore.kernel.org/r/20231019-strncpy-drivers-nvdimm-btt-c-v2-1-366993878cf0@google.com Signed-off-by: Kees Cook --- drivers/nvdimm/btt.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/nvdimm/btt.c b/drivers/nvdimm/btt.c index d5593b0dc700..9372c36e8f76 100644 --- a/drivers/nvdimm/btt.c +++ b/drivers/nvdimm/btt.c @@ -986,7 +986,7 @@ static int btt_arena_write_layout(struct arena_info *arena) if (!super) return -ENOMEM; - strncpy(super->signature, BTT_SIG, BTT_SIG_LEN); + strscpy(super->signature, BTT_SIG, sizeof(super->signature)); export_uuid(super->uuid, nd_btt->uuid); export_uuid(super->parent_uuid, parent_uuid); super->flags = cpu_to_le32(arena->flags);