Hi, On Tue, Aug 18, 2026 at 1:55 AM David Laight <[email protected]> wrote: > > On Fri, 14 Aug 2026 00:28:45 -0700 > Mariia Nikitash <[email protected]> wrote: > > > In preparation for removing the deprecated strlcat() API[1], replace its > > uses in root_nfs_cat() with snprintf(). > > > > Build the separator and source string in a single call using the > > remaining space in the destination buffer. snprintf() returns the length > > it would have written excluding the terminating NUL, so comparing the > > return value against the remaining buffer space preserves the existing > > truncation check. > > > > Link: https://github.com/KSPP/linux/issues/370 [1] > > Signed-off-by: Mariia Nikitash <[email protected]> > > --- > > fs/nfs/nfsroot.c | 8 ++++---- > > 1 file changed, 4 insertions(+), 4 deletions(-) > > > > diff --git a/fs/nfs/nfsroot.c b/fs/nfs/nfsroot.c > > index 432612d22437..e951fe731679 100644 > > --- a/fs/nfs/nfsroot.c > > +++ b/fs/nfs/nfsroot.c > > @@ -173,12 +173,12 @@ static int __init root_nfs_cat(char *dest, const char > > *src, > > const size_t destlen) > > { > > size_t len = strlen(dest); > > + size_t remaining = destlen - len; > > + const char *sep = ""; > > > > if (len && dest[len - 1] != ',') > > - if (strlcat(dest, ",", destlen) >= destlen) > > - return -1; > > - > > - if (strlcat(dest, src, destlen) >= destlen) > > + sep = ","; > > + if (snprintf(dest + len, remaining, "%s%s", sep, src) >= remaining) > > return -1; > > I think I'd have gone for: > size_t len = strlen(dest); > if (len && dest[len - 1] != ',' && ++len < destlen) > dest[len - 1] = ','; > if (strscpy(dest + len, src, destlen - len) < 0) > return -1;
Can we run into underflow issues if `len == destlen` during the increment. imagine @len is 10 and @destlen is also 10. We end up incrementing len and our strscpy receives `10 - 11` wrapping to SIZE_MAX. Maybe this isn't reachable as @destlen may always be larger than what `strlen()` can give us but that increment looks suspicious. > > Although it would be better as an 'add_option()' function. > I suspect the it used to be just strcat(). > (similarly for root_nfs_copy() which is a pointless wrapper on strscpy()). > > Much more worth while would be fixing the sprintf() for NFS_ROOT. > > David > > > return 0; > > } > Justin
