Karel Zak <kzak@xxxxxxxxxx> writes: > On Mon, Oct 03, 2016 at 10:05:03PM +0200, Tobias Stoeckmann wrote: >> A strlen() call can lead to out of boundary read access if the >> superblock in question has no nul-bytes after the string. This >> could be avoided by using strnlen() but the calls in question >> merely existed to check if the string length is not 0. >> >> By changing the calls as proposed with this diff, these files are >> in sync with other superblock files, which do exactly the same. >> --- >> libblkid/src/superblocks/befs.c | 2 +- >> libblkid/src/superblocks/ext.c | 2 +- >> libblkid/src/superblocks/jfs.c | 2 +- >> libblkid/src/superblocks/nilfs.c | 2 +- >> libblkid/src/superblocks/romfs.c | 2 +- >> libblkid/src/superblocks/xfs.c | 2 +- >> 6 files changed, 6 insertions(+), 6 deletions(-) > > Applied, thanks. > >> diff --git a/libblkid/src/superblocks/befs.c b/libblkid/src/superblocks/befs.c >> index 7e9eaf6..36e079f 100644 >> --- a/libblkid/src/superblocks/befs.c >> +++ b/libblkid/src/superblocks/befs.c >> @@ -451,7 +451,7 @@ static int probe_befs(blkid_probe pr, const struct blkid_idmag *mag) >> /* >> * all checks pass, set LABEL, VERSION and UUID >> */ >> - if (strlen(bs->name)) >> + if (*bs->name != '\0') > > Good catch, I hate it too. BTW, you can use > > if (*bs->name) > > it's enough. Interesting to note that GCC compiles it both to the same instructions: https://godbolt.org/g/adKv1I #include <string.h> int code1(const char *s) { if(strlen(s)) return 1; return 0; } int code2(const char *s) { if(*s) return 1; return 0; } code1(char const*): push rbp mov rbp, rsp mov QWORD PTR [rbp-8], rdi mov rax, QWORD PTR [rbp-8] movzx eax, BYTE PTR [rax] test al, al je .L2 mov eax, 1 jmp .L3 .L2: mov eax, 0 .L3: pop rbp ret code2(char const*): push rbp mov rbp, rsp mov QWORD PTR [rbp-8], rdi mov rax, QWORD PTR [rbp-8] movzx eax, BYTE PTR [rax] test al, al je .L5 mov eax, 1 jmp .L6 .L5: mov eax, 0 .L6: pop rbp ret -- Aurélien Aptel / SUSE Labs Samba Team GPG: 1839 CB5F 9F5B FB9B AA97 8C99 03C8 A49B 521B D5D3 SUSE Linux GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) -- To unsubscribe from this list: send the line "unsubscribe util-linux" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
