ext3: fix start and len arguments handling in ext3_trim_fs()

The overflow might happen when passing blocknr into
ext3_get_group_no_and_offset(), because it expects type ext3_fsblk_t
which might be smaller than uint64_t. This will most likely happen when
calling FITRIM with the default argument len = ULLONG_MAX.

Fix this by using "end" variable instead of "start+len" as it is easier
to get right and specifically check that the end is not beyond the end
of the file system, so we are sure that the result of
get_group_no_and_offset() will not overflow. Otherwise truncate it to
the size of the file system.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Jan Kara <jack@suse.cz>

diff --git a/fs/ext3/balloc.c b/fs/ext3/balloc.c
index 954a7d355f59305f034c0787bae014ca6c8580aa..1e036b79384c214f517c052de529932069d39dd0 100644 (file)
--- a/fs/ext3/balloc.c
+++ b/fs/ext3/balloc.c
@@ -1973,7 +1973,7 @@ static ext3_grpblk_t ext3_trim_all_free(struct super_block *sb,
        sbi = EXT3_SB(sb);
 
         /* Walk through the whole group */
-       while (start < max) {
+       while (start <= max) {
                start = bitmap_search_next_usable_block(start, bitmap_bh, max);
                if (start < 0)
                        break;
@@ -1983,7 +1983,7 @@ static ext3_grpblk_t ext3_trim_all_free(struct super_block *sb,
                 * Allocate contiguous free extents by setting bits in the
                 * block bitmap
                 */
-               while (next < max
+               while (next <= max
                        && claim_block(sb_bgl_lock(sbi, group),
                                        next, bitmap_bh)) {
                        next++;
@@ -2094,73 +2094,74 @@ err_out:
  */
 int ext3_trim_fs(struct super_block *sb, struct fstrim_range *range)
 {
-       ext3_grpblk_t last_block, first_block, free_blocks;
-       unsigned long first_group, last_group;
-       unsigned long group, ngroups;
+       ext3_grpblk_t last_block, first_block;
+       unsigned long group, first_group, last_group;
        struct ext3_group_desc *gdp;
        struct ext3_super_block *es = EXT3_SB(sb)->s_es;
-       uint64_t start, len, minlen, trimmed;
+       uint64_t start, minlen, end, trimmed = 0;
+       ext3_fsblk_t first_data_blk =
+                       le32_to_cpu(EXT3_SB(sb)->s_es->s_first_data_block);
        ext3_fsblk_t max_blks = le32_to_cpu(es->s_blocks_count);
        int ret = 0;
 
-       start = (range->start >> sb->s_blocksize_bits) +
-               le32_to_cpu(es->s_first_data_block);
-       len = range->len >> sb->s_blocksize_bits;
+       start = range->start >> sb->s_blocksize_bits;
+       end = start + (range->len >> sb->s_blocksize_bits) - 1;
        minlen = range->minlen >> sb->s_blocksize_bits;
-       trimmed = 0;
 
-       if (unlikely(minlen > EXT3_BLOCKS_PER_GROUP(sb)))
+       if (unlikely(minlen > EXT3_BLOCKS_PER_GROUP(sb)) ||
+           unlikely(start >= max_blks))
                return -EINVAL;
-       if (start >= max_blks)
-               return -EINVAL;
-       if (start + len > max_blks)
-               len = max_blks - start;
+       if (end >= max_blks)
+               end = max_blks - 1;
+       if (end <= first_data_blk)
+               goto out;
+       if (start < first_data_blk)
+               start = first_data_blk;
 
-       ngroups = EXT3_SB(sb)->s_groups_count;
        smp_rmb();
 
        /* Determine first and last group to examine based on start and len */
        ext3_get_group_no_and_offset(sb, (ext3_fsblk_t) start,
                                     &first_group, &first_block);
-       ext3_get_group_no_and_offset(sb, (ext3_fsblk_t) (start + len),
+       ext3_get_group_no_and_offset(sb, (ext3_fsblk_t) end,
                                     &last_group, &last_block);
-       last_group = (last_group > ngroups - 1) ? ngroups - 1 : last_group;
-       last_block = EXT3_BLOCKS_PER_GROUP(sb);
 
-       if (first_group > last_group)
-               return -EINVAL;
+       /* end now represents the last block to discard in this group */
+       end = EXT3_BLOCKS_PER_GROUP(sb) - 1;
 
        for (group = first_group; group <= last_group; group++) {
                gdp = ext3_get_group_desc(sb, group, NULL);
                if (!gdp)
                        break;
 
-               free_blocks = le16_to_cpu(gdp->bg_free_blocks_count);
-               if (free_blocks < minlen)
-                       continue;
-
                /*
                 * For all the groups except the last one, last block will
-                * always be EXT3_BLOCKS_PER_GROUP(sb), so we only need to
-                * change it for the last group in which case first_block +
-                * len < EXT3_BLOCKS_PER_GROUP(sb).
+                * always be EXT3_BLOCKS_PER_GROUP(sb)-1, so we only need to
+                * change it for the last group, note that last_block is
+                * already computed earlier by ext3_get_group_no_and_offset()
                 */
-               if (first_block + len < EXT3_BLOCKS_PER_GROUP(sb))
-                       last_block = first_block + len;
-               len -= last_block - first_block;
+               if (group == last_group)
+                       end = last_block;
 
-               ret = ext3_trim_all_free(sb, group, first_block,
-                                       last_block, minlen);
-               if (ret < 0)
-                       break;
+               if (le16_to_cpu(gdp->bg_free_blocks_count) >= minlen) {
+                       ret = ext3_trim_all_free(sb, group, first_block,
+                                                end, minlen);
+                       if (ret < 0)
+                               break;
+                       trimmed += ret;
+               }
 
-               trimmed += ret;
+               /*
+                * For every group except the first one, we are sure
+                * that the first block to discard will be block #0.
+                */
                first_block = 0;
        }
 
-       if (ret >= 0)
+       if (ret > 0)
                ret = 0;
-       range->len = trimmed * sb->s_blocksize;
 
+out:
+       range->len = trimmed * sb->s_blocksize;
        return ret;
 }