On Fri, Oct 10, 2025 at 03:48:48PM -0700, Kees Cook wrote: > On Fri, Oct 10, 2025 at 06:13:41PM +0200, Thorsten Blum wrote: > > strncpy() is deprecated for NUL-terminated destination buffers; use > > strscpy_pad() instead to retain the zero-padding behavior of strncpy(). > > > > strscpy_pad() automatically determines the size of the fixed-length > > destination buffer via sizeof() when the optional size argument is > > omitted, making an explicit size unnecessary. > > I would explicitly say that the old code was NUL terminating the buffer > due to it being "ECRYPTFS_PASSWORD_SIG_SIZE + 1" sized with strncpy > left to fill ECRYPTFS_PASSWORD_SIG_SIZE. And then you have to answer the > question, "how was this initialized?" and trace it back to: > > epayload = kzalloc(sizeof(*epayload) + payload_datalen + > datablob_len + HASH_SIZE + 1, GFP_KERNEL); > > so the final byte was always being zeroed there, but now we're > explicitly zeroing it (good). So there _is_ a functional change (we're > writing 1 more byte here now), but it's more robust that way. There is > no expected _logical_ change, though, yes.
Thanks for the remarks. Thorsten, would you mind posting +1 with the commit message changes, and reviewed-by tags (from me and Kees). > > > > > In encrypted_init(), the source string 'key_desc' is validated by > > valid_ecryptfs_desc() before calling ecryptfs_fill_auth_tok(), and is > > therefore NUL-terminated and satisfies the __must_be_cstr() requirement > > of strscpy_pad(). > > > > No functional changes. [just as reminder: removing this sentence was my earlier remark] > > > > Link: https://github.com/KSPP/linux/issues/90 > > Signed-off-by: Thorsten Blum <[email protected]> > > With "ECRYPTFS_PASSWORD_SIG_SIZE + 1" and tracing of the destination > buffer initialization added to the commit log: > > Reviewed-by: Kees Cook <[email protected]> > > -Kees > > -- > Kees Cook BR, Jarkko
