| Message ID | 20230823-strncpy-block-partitions-cmdline-ibm-v2-1-40c77f7182fc@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] partitions/ibm: refactor deprecated strncpy | expand |
On Wed, Aug 23, 2023 at 09:24:22PM +0000, Justin Stitt wrote: > `strncpy` is deprecated [1] and we should favor different interfaces. > > A suitable replacement is `strtomem_pad` as it is a more robust and less > ambiguous interface. In this case, the destination buffer is not > necessarily NUL-terminated as Heiko points out [2]. Using `strtomem_pad` > over strncpy means it is now more obvious what is expected of the > destination buffer: 1) Not necessarily NUL-terminated and 2) padded with > NUL-bytes > > Link: www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings[1] > Link: https://lore.kernel.org/all/20230823134936.14378-E-hca@linux.ibm.com/ [2] > Link: https://github.com/KSPP/linux/issues/90 > Suggested-by: Kees Cook <keescook@chromium.org> > Cc: linux-hardening@vger.kernel.org > Signed-off-by: Justin Stitt <justinstitt@google.com> > --- > Changes in v2: > - prefer `strtomem_pad` over `strscpy` (thanks Kees) > - Link to v1: https://lore.kernel.org/r/20230822-strncpy-block-partitions-cmdline-ibm-v1-1-154dea8f755c@google.com > --- > block/partitions/ibm.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/block/partitions/ibm.c b/block/partitions/ibm.c > index 403756dbd50d..56c076c5523d 100644 > --- a/block/partitions/ibm.c > +++ b/block/partitions/ibm.c > @@ -111,11 +111,11 @@ static int find_label(struct parsed_partitions *state, > !strcmp(temp, "LNX1") || > !strcmp(temp, "CMS1")) { > if (!strcmp(temp, "VOL1")) { > - strncpy(type, label->vol.vollbl, 4); > - strncpy(name, label->vol.volid, 6); > + strtomem_pad(type, label->vol.vollbl, 4); > + strtomem_pad(name, label->vol.volid, 6); > } else { > - strncpy(type, label->lnx.vollbl, 4); > - strncpy(name, label->lnx.volid, 6); > + strtomem_pad(type, label->lnx.vollbl, 4); > + strtomem_pad(name, label->lnx.volid, 6); > } > EBCASC(type, 4); > EBCASC(name, 6); This won't compile if find_label() is not inlined due the BUILD_BUG_ON() within strtomem_pad(). However instead of sending new versions, I think it would be better to ask Stefan and Jan to have a look at this. I think there is room for improvement with the string handling besides getting rid of strncpy(). And they know best the semantics of the (non-)strings.
diff --git a/block/partitions/ibm.c b/block/partitions/ibm.c index 403756dbd50d..56c076c5523d 100644 --- a/block/partitions/ibm.c +++ b/block/partitions/ibm.c @@ -111,11 +111,11 @@ static int find_label(struct parsed_partitions *state, !strcmp(temp, "LNX1") || !strcmp(temp, "CMS1")) { if (!strcmp(temp, "VOL1")) { - strncpy(type, label->vol.vollbl, 4); - strncpy(name, label->vol.volid, 6); + strtomem_pad(type, label->vol.vollbl, 4); + strtomem_pad(name, label->vol.volid, 6); } else { - strncpy(type, label->lnx.vollbl, 4); - strncpy(name, label->lnx.volid, 6); + strtomem_pad(type, label->lnx.vollbl, 4); + strtomem_pad(name, label->lnx.volid, 6); } EBCASC(type, 4); EBCASC(name, 6);
`strncpy` is deprecated [1] and we should favor different interfaces. A suitable replacement is `strtomem_pad` as it is a more robust and less ambiguous interface. In this case, the destination buffer is not necessarily NUL-terminated as Heiko points out [2]. Using `strtomem_pad` over strncpy means it is now more obvious what is expected of the destination buffer: 1) Not necessarily NUL-terminated and 2) padded with NUL-bytes Link: www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings[1] Link: https://lore.kernel.org/all/20230823134936.14378-E-hca@linux.ibm.com/ [2] Link: https://github.com/KSPP/linux/issues/90 Suggested-by: Kees Cook <keescook@chromium.org> Cc: linux-hardening@vger.kernel.org Signed-off-by: Justin Stitt <justinstitt@google.com> --- Changes in v2: - prefer `strtomem_pad` over `strscpy` (thanks Kees) - Link to v1: https://lore.kernel.org/r/20230822-strncpy-block-partitions-cmdline-ibm-v1-1-154dea8f755c@google.com --- block/partitions/ibm.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) --- base-commit: 706a741595047797872e669b3101429ab8d378ef change-id: 20230822-strncpy-block-partitions-cmdline-ibm-7f5bcca507ea Best regards, -- Justin Stitt <justinstitt@google.com>