fs/ntfs3: Correct function is_rst_area_valid

Reported-by: Robert Morris <rtm@csail.mit.edu>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>

diff --git a/fs/ntfs3/fslog.c b/fs/ntfs3/fslog.c
index 7dbb000fc69113a78df7c050c43e27b69cac33c2..855519713bf79074ed336ca7094cca5d5cdbc009 100644 (file)
--- a/fs/ntfs3/fslog.c
+++ b/fs/ntfs3/fslog.c
@@ -465,7 +465,7 @@ static inline bool is_rst_area_valid(const struct RESTART_HDR *rhdr)
 {
        const struct RESTART_AREA *ra;
        u16 cl, fl, ul;
-       u32 off, l_size, file_dat_bits, file_size_round;
+       u32 off, l_size, seq_bits;
        u16 ro = le16_to_cpu(rhdr->ra_off);
        u32 sys_page = le32_to_cpu(rhdr->sys_page_size);
 
@@ -511,13 +511,15 @@ static inline bool is_rst_area_valid(const struct RESTART_HDR *rhdr)
        /* Make sure the sequence number bits match the log file size. */
        l_size = le64_to_cpu(ra->l_size);
 
-       file_dat_bits = sizeof(u64) * 8 - le32_to_cpu(ra->seq_num_bits);
-       file_size_round = 1u << (file_dat_bits + 3);
-       if (file_size_round != l_size &&
-           (file_size_round < l_size || (file_size_round / 2) > l_size)) {
-               return false;
+       seq_bits = sizeof(u64) * 8 + 3;
+       while (l_size) {
+               l_size >>= 1;
+               seq_bits -= 1;
        }
 
+       if (seq_bits != ra->seq_num_bits)
+               return false;
+
        /* The log page data offset and record header length must be quad-aligned. */
        if (!IS_ALIGNED(le16_to_cpu(ra->data_off), 8) ||
            !IS_ALIGNED(le16_to_cpu(ra->rec_hdr_len), 8))