| Message ID | 20240328-strncpy-fs-reiserfs-item_ops-c-v1-1-2dab6d22a996@google.com (mailing list archive) |
|---|---|
| State | Mainlined |
| Commit | 31ca7e77fd7efc3f98582bf682fcaadc31a7d505 |
| Headers | show |
| Series | reiserfs: replace deprecated strncpy with scnprintf | expand |
On Thu, Mar 28, 2024 at 09:16:52PM +0000, Justin Stitt wrote: > strncpy() is deprecated for use on NUL-terminated destination strings > [1] and as such we should prefer more robust and less ambiguous string > interfaces. > > Our goal here is to get @namebuf populated with @name's contents but > surrounded with quotes. There is some careful handling done to ensure we > properly truncate @name so that we have room for a literal quote as well > as a NUL-term. All this careful handling can be done with scnprintf > using the dynamic string width specifier %.*s which allows us to pass in > the max size for a source string. Doing this, we can put literal quotes > in our format specifier and ensure @name is truncated to fit inbetween > these quotes (-3 is from 2 quotes + 1 NUL-byte). > > All in all, we get to remove a deprecated use of strncpy and clean up > this code nicely! > > 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 <justinstitt@google.com> Yeah, I like the use of %.*s here. This is much more clear now I think. Reviewed-by: Kees Cook <keescook@chromium.org>
On Thu, 28 Mar 2024 21:16:52 +0000, Justin Stitt wrote: > strncpy() is deprecated for use on NUL-terminated destination strings > [1] and as such we should prefer more robust and less ambiguous string > interfaces. > > Our goal here is to get @namebuf populated with @name's contents but > surrounded with quotes. There is some careful handling done to ensure we > properly truncate @name so that we have room for a literal quote as well > as a NUL-term. All this careful handling can be done with scnprintf > using the dynamic string width specifier %.*s which allows us to pass in > the max size for a source string. Doing this, we can put literal quotes > in our format specifier and ensure @name is truncated to fit inbetween > these quotes (-3 is from 2 quotes + 1 NUL-byte). > > [...] Applied to for-next/hardening, thanks! [1/1] reiserfs: replace deprecated strncpy with scnprintf https://git.kernel.org/kees/c/ba287092ae90 Take care,
diff --git a/fs/reiserfs/item_ops.c b/fs/reiserfs/item_ops.c index 3a5a752d96c7..5011c10287c6 100644 --- a/fs/reiserfs/item_ops.c +++ b/fs/reiserfs/item_ops.c @@ -389,16 +389,9 @@ static void direntry_print_item(struct item_head *ih, char *item) name = item + deh_location(deh); if (name[namelen - 1] == 0) namelen = strlen(name); - namebuf[0] = '"'; - if (namelen > sizeof(namebuf) - 3) { - strncpy(namebuf + 1, name, sizeof(namebuf) - 3); - namebuf[sizeof(namebuf) - 2] = '"'; - namebuf[sizeof(namebuf) - 1] = 0; - } else { - memcpy(namebuf + 1, name, namelen); - namebuf[namelen + 1] = '"'; - namebuf[namelen + 2] = 0; - } + + scnprintf(namebuf, sizeof(namebuf), "\"%.*s\"", + (int)sizeof(namebuf)-3, name); printk("%d: %-15s%-15d%-15d%-15lld%-15lld(%s)\n", i, namebuf,
strncpy() is deprecated for use on NUL-terminated destination strings [1] and as such we should prefer more robust and less ambiguous string interfaces. Our goal here is to get @namebuf populated with @name's contents but surrounded with quotes. There is some careful handling done to ensure we properly truncate @name so that we have room for a literal quote as well as a NUL-term. All this careful handling can be done with scnprintf using the dynamic string width specifier %.*s which allows us to pass in the max size for a source string. Doing this, we can put literal quotes in our format specifier and ensure @name is truncated to fit inbetween these quotes (-3 is from 2 quotes + 1 NUL-byte). All in all, we get to remove a deprecated use of strncpy and clean up this code nicely! 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 <justinstitt@google.com> --- I realize this file has been marked as "obsolete" as told by checkpatch: | WARNING: fs/reiserfs/item_ops.c is marked as 'obsolete' in the MAINTAINERS hierarchy. No unnecessary modifications please. ... but I really want to remove ALL instances of strncpy so we can rip it out of the kernel as per: https://github.com/KSPP/linux/issues/90. --- fs/reiserfs/item_ops.c | 13 +++---------- 1 file changed, 3 insertions(+), 10 deletions(-) --- base-commit: 928a87efa42302a23bb9554be081a28058495f22 change-id: 20240328-strncpy-fs-reiserfs-item_ops-c-c2f9b8a6c1f3 Best regards, -- Justin Stitt <justinstitt@google.com>