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libsparse: use strcmp and validate last_used pointer 

This patch is used to fix two Bugs in backed_block.c

First, fix wrong comparing string way: we should use strcmp rather than
just compare their address. Second, fix using illegal memory risk in
bbl->last_used pointer. When entering queue_bb function,
bbl->last_used = new_bb, but in the following code if
queue_bb(xx, bb, new_bb) return ok, the space of new_bb is released. So
next time, if you use bbl->last_used pointer, may cause segment fault !

Change-Id: I6abb505f9b903b697448639fc64fb7518df5cca1
This commit is contained in:
lei wang wang 2015-08-21 11:13:46 +08:00 committed by Mark Salyzyn
parent dcf890914c
commit c227a1d855
1 changed files with 6 additions and 2 deletions
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8
libsparse/backed_block.c
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@ -221,7 +221,8 @@ static int merge_bb(struct backed_block_list *bbl,
}
break;
case BACKED_BLOCK_FILE:
if (a->file.filename != b->file.filename ||
/* Already make sure b->type is BACKED_BLOCK_FILE */
if (strcmp(a->file.filename, b->file.filename) ||
a->file.offset + a->len != b->file.offset) {
return -EINVAL;
}
@ -279,7 +280,10 @@ static int queue_bb(struct backed_block_list *bbl, struct backed_block *new_bb)
}
merge_bb(bbl, new_bb, new_bb->next);
merge_bb(bbl, bb, new_bb);
if (!merge_bb(bbl, bb, new_bb)) {
/* new_bb destroyed, point to retained as last_used */
bbl->last_used = bb;
}
return 0;
}