Change OPT_STR max value to be 1 less than the "ARRAY_SIZE" of "_choices" array. As a result, remove -1 from (opt->max-1) in bch2_opt_to_text.
The "_choices" array is a null-terminated array, so computing the maximum using "ARRAY_SIZE" without subtracting 1 yields an incorrect result. Since bch2_opt_validate don't subtract 1, as bch2_opt_to_text does, values bigger than the actual maximum would pass through option validation. Reported-by: [email protected] Closes: https://syzkaller.appspot.com/bug?extid=bee87a0c3291c06aa8c6 Fixes: 63c4b2545382 ("bcachefs: Better superblock opt validation") Suggested-by: Kent Overstreet <[email protected]> Signed-off-by: Piotr Zalewski <[email protected]> --- Notes: Changes in v2: - Instead of subtracting 1 in bch2_opt_validate as in bch2_opt_to_text add -1 in OPT_STR macro definition and remove subtraction in bch2_opt_to_text. link to v1: https://lore.kernel.org/linux-bcachefs/[email protected]/ fs/bcachefs/opts.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/bcachefs/opts.c b/fs/bcachefs/opts.c index 83f55cf99d46..49c59aec6954 100644 --- a/fs/bcachefs/opts.c +++ b/fs/bcachefs/opts.c @@ -227,7 +227,7 @@ const struct bch_option bch2_opt_table[] = { #define OPT_UINT(_min, _max) .type = BCH_OPT_UINT, \ .min = _min, .max = _max #define OPT_STR(_choices) .type = BCH_OPT_STR, \ - .min = 0, .max = ARRAY_SIZE(_choices), \ + .min = 0, .max = ARRAY_SIZE(_choices) - 1, \ .choices = _choices #define OPT_STR_NOLIMIT(_choices) .type = BCH_OPT_STR, \ .min = 0, .max = U64_MAX, \ @@ -429,7 +429,7 @@ void bch2_opt_to_text(struct printbuf *out, prt_printf(out, "%lli", v); break; case BCH_OPT_STR: - if (v < opt->min || v >= opt->max - 1) + if (v < opt->min || v >= opt->max) prt_printf(out, "(invalid option %lli)", v); else if (flags & OPT_SHOW_FULL_LIST) prt_string_option(out, opt->choices, v); -- 2.47.0
