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Fix signedness mismatch and integer underflow

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persist_get_max_entries() is supposed to return an unsigned integer as the
maximum number of entries but it also wrongly returns "-1" as an error
condition. Also fix an issue where an unsigned subtraction in this routine
could lead to integer underflow.

Bug: 112731440
Test: manual
Change-Id: I9672e39bef2c12156dda7806a08c52044962c178
This commit is contained in:
Rubin Xu 2018-10-09 16:13:38 +01:00 committed by Paul Crowley
parent 6aaedb0dca
commit f83cc61c1f
1 changed files with 7 additions and 6 deletions
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13
cryptfs.cpp
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@ -2458,24 +2458,25 @@ int cryptfs_changepw(int crypt_type, const char* newpw) {
static unsigned int persist_get_max_entries(int encrypted) {
struct crypt_mnt_ftr crypt_ftr;
unsigned int dsize;
unsigned int max_persistent_entries;
/* If encrypted, use the values from the crypt_ftr, otherwise
* use the values for the current spec.
*/
if (encrypted) {
if (get_crypt_ftr_and_key(&crypt_ftr)) {
return -1;
/* Something is wrong, assume no space for entries */
return 0;
}
dsize = crypt_ftr.persist_data_size;
} else {
dsize = CRYPT_PERSIST_DATA_SIZE;
}
max_persistent_entries =
(dsize - sizeof(struct crypt_persist_data)) / sizeof(struct crypt_persist_entry);
return max_persistent_entries;
if (dsize > sizeof(struct crypt_persist_data)) {
return (dsize - sizeof(struct crypt_persist_data)) / sizeof(struct crypt_persist_entry);
} else {
return 0;
}
}
static int persist_get_key(const char* fieldname, char* value) {