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btrfs-progs: don't overrun "answer" array in cmds-chunk.c 

Eric noticed the trivial stack overflow bug in ask_user().  I went to
see the context for that fix and found that ask_user() was a bit much.

This fixes the overflow bug that Eric found, endless spinning on scanf()
errors, removes dead code, and leaves us with a trivial helper.

Signed-off-by: Zach Brown <zab@redhat.com>
Signed-off-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
This commit is contained in:
Zach Brown 2013-08-06 11:49:04 -07:00 committed by David Sterba
parent 689ad3e362
commit 6a0af4e57b
1 changed files with 14 additions and 51 deletions
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65
cmds-chunk.c
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@ -1307,58 +1307,22 @@ fail_close_fd:
return ret;
}
static int ask_user(char *question, int defval)
/*
* This reads a line from the stdin and only returns non-zero if the
* first whitespace delimited token is a case insensitive match with yes
* or y.
*/
static int ask_user(char *question)
{
char answer[5];
char *defstr;
int i;
char buf[30] = {0,};
char *saveptr = NULL;
char *answer;
if (defval == 1)
defstr = "[Y/n]";
else if (defval == 0)
defstr = "[y/N]";
else if (defval == -1)
defstr = "[y/n]";
else
BUG_ON(1);
again:
printf("%s%s? ", question, defstr);
printf("%s [y/N]: ", question);
i = 0;
while (i < 4 && scanf("%c", &answer[i])) {
if (answer[i] == '\n') {
answer[i] = '\0';
break;
} else if (answer[i] == ' '){
answer[i] = '\0';
if (i == 0)
continue;
else
break;
} else if (answer[i] >= 'A' && answer[i] <= 'Z') {
answer[i] += 'a' - 'A';
}
i++;
}
answer[5] = '\0';
__fpurge(stdin);
if (strlen(answer) == 0) {
if (defval != -1)
return defval;
else
goto again;
}
if (!strcmp(answer, "yes") ||
!strcmp(answer, "y"))
return 1;
if (!strcmp(answer, "no") ||
!strcmp(answer, "n"))
return 0;
goto again;
return fgets(buf, sizeof(buf) - 1, stdin) &&
(answer = strtok_r(buf, " \t\n\r", &saveptr)) &&
(!strcasecmp(answer, "yes") || !strcasecmp(answer, "y"));
}
static int btrfs_get_device_extents(u64 chunk_object,
@ -1752,8 +1716,7 @@ static int btrfs_recover_chunk_tree(char *path, int verbose, int yes)
}
if (!rc.yes) {
ret = ask_user("We are going to rebuild the chunk tree on disk, it might destroy the old metadata on the disk, Are you sure",
0);
ret = ask_user("We are going to rebuild the chunk tree on disk, it might destroy the old metadata on the disk, Are you sure?");
if (!ret) {
ret = BTRFS_CHUNK_TREE_REBUILD_ABORTED;
goto fail_close_ctree;