134c53098
Denys Vlasenko
2015-01-03
Subject
libpwdgrp: store getXXnam result in a single malloc block
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libpwdgrp/pwd_grp.c+32 -26
| @@ -34,24 +34,21 @@ | |
| struct const_passdb { | |
| const char *filename; | |
| - | const char def[9]; |
| - | const uint8_t off[9]; |
| + | const char def[7 + 2*ENABLE_USE_BB_SHADOW]; |
| + | const uint8_t off[7 + 2*ENABLE_USE_BB_SHADOW]; |
| uint8_t numfields; | |
| + | uint8_t size_of; |
| }; | |
| struct passdb { | |
| const char *filename; | |
| - | const char def[9]; |
| - | const uint8_t off[9]; |
| + | const char def[7 + 2*ENABLE_USE_BB_SHADOW]; |
| + | const uint8_t off[7 + 2*ENABLE_USE_BB_SHADOW]; |
| uint8_t numfields; | |
| + | uint8_t size_of; |
| FILE *fp; | |
| char *malloced; | |
| - | char struct_result[ |
| - | /* Should be max(sizeof passwd,group,spwd), but this will do: */ |
| - | IF_NOT_USE_BB_SHADOW(sizeof(struct passwd)) |
| - | IF_USE_BB_SHADOW(sizeof(struct spwd)) |
| - | ]; |
| }; | |
| - | /* Note: for shadow db, def[9] will not contain terminating NUL, |
| + | /* Note: for shadow db, def[] will not contain terminating NUL, |
| * but convert_to_struct() logic detects def[] end by "less than SP?", | |
| * not by "is it NUL?" condition; and off[0] happens to be zero | |
| * for every db anyway, so there _is_ in fact a terminating NUL there. | |
| @@ -76,7 +73,7 @@ static const struct const_passdb const_pw_db = { | |
| offsetof(struct passwd, pw_dir), /* 5 S */ | |
| offsetof(struct passwd, pw_shell) /* 6 S */ | |
| }, | |
| - | sizeof(PW_DEF)-1 |
| + | sizeof(PW_DEF)-1, sizeof(struct passwd) |
| }; | |
| static const struct const_passdb const_gr_db = { | |
| _PATH_GROUP, GR_DEF, | |
| @@ -86,7 +83,7 @@ static const struct const_passdb const_gr_db = { | |
| offsetof(struct group, gr_gid), /* 2 I */ | |
| offsetof(struct group, gr_mem) /* 3 m (char **) */ | |
| }, | |
| - | sizeof(GR_DEF)-1 |
| + | sizeof(GR_DEF)-1, sizeof(struct group) |
| }; | |
| #if ENABLE_USE_BB_SHADOW | |
| static const struct const_passdb const_sp_db = { | |
| @@ -102,19 +99,20 @@ static const struct const_passdb const_sp_db = { | |
| offsetof(struct spwd, sp_expire), /* 7 l */ | |
| offsetof(struct spwd, sp_flag) /* 8 r Reserved */ | |
| }, | |
| - | sizeof(SP_DEF)-1 |
| + | sizeof(SP_DEF)-1, sizeof(struct spwd) |
| }; | |
| #endif | |
| /* We avoid having big global data. */ | |
| struct statics { | |
| - | /* It's ok to use same buffer (db[0].struct_result) for getpwuid and getpwnam. |
| + | /* It's ok to use same buffer (db[0].malloced) for getpwuid and getpwnam. |
| * Manpage says: | |
| * "The return value may point to a static area, and may be overwritten | |
| * by subsequent calls to getpwent(), getpwnam(), or getpwuid()." | |
| */ | |
| struct passdb db[2 + ENABLE_USE_BB_SHADOW]; | |
| char *tokenize_end; | |
| + | unsigned string_size; |
| }; | |
| static struct statics *ptr_to_statics; | |
| @@ -205,21 +203,21 @@ static char *parse_common(FILE *fp, const char *filename, | |
| bb_error_msg("bad record at %s:%u", filename, count); | |
| goto free_and_next; | |
| } | |
| + | S.string_size = S.tokenize_end - buf; |
| - | /* Ugly hack: group db requires aqdditional buffer space |
| + | /* Ugly hack: group db requires additional buffer space |
| * for members[] array. If there is only one group, we need space | |
| * for 3 pointers: alignment padding, group name, NULL. | |
| * +1 for every additional group. | |
| */ | |
| if (n_fields == sizeof(GR_DEF)-1) { /* if we read group file */ | |
| - | int resize = 3; |
| + | int cnt = 3; |
| char *p = buf; | |
| while (*p) | |
| if (*p++ == ',') | |
| - | resize++; |
| - | resize *= sizeof(char**); |
| - | resize += S.tokenize_end - buf; |
| - | buf = xrealloc(buf, resize); |
| + | cnt++; |
| + | S.string_size += cnt * sizeof(char*); |
| + | buf = xrealloc(buf, S.string_size); |
| } | |
| if (!key) { | |
| @@ -258,8 +256,8 @@ static void *convert_to_struct(struct passdb *db, | |
| const char *def = db->def; | |
| const uint8_t *off = db->off; | |
| - | /* TODO? for consistency, zero out all fields */ |
| - | /* memset(result, 0, size_of_result);*/ |
| + | /* For consistency, zero out all fields */ |
| + | memset(result, 0, db->size_of); |
| for (;;) { | |
| void *member = (char*)result + (*off++); | |
| @@ -305,7 +303,7 @@ static void *convert_to_struct(struct passdb *db, | |
| /* def "r" does nothing */ | |
| def++; | |
| - | if ((unsigned char)*def < (unsigned char)' ') |
| + | if ((unsigned char)*def <= (unsigned char)' ') |
| break; | |
| buffer += strlen(buffer) + 1; | |
| } | |
| @@ -328,7 +326,9 @@ static int FAST_FUNC getXXnam_r(const char *name, uintptr_t db_and_field_pos, | |
| db = &S.db[db_and_field_pos >> 2]; | |
| *(void**)result = NULL; | |
| - | buf = parse_file(db->filename, db->numfields, name, db_and_field_pos & 3); |
| + | buf = parse_file(db->filename, db->numfields, name, 0 /*db_and_field_pos & 3*/); |
| + | /* "db_and_field_pos & 3" is commented out since so far we don't implement |
| + | * getXXXid_r() functions which would use that to pass 2 here */ |
| if (buf) { | |
| size_t size = S.tokenize_end - buf; | |
| if (size > buflen) { | |
| @@ -433,8 +433,14 @@ static void* FAST_FUNC getXXnam(const char *name, unsigned db_and_field_pos) | |
| buf = parse_common(db->fp, db->filename, db->numfields, name, db_and_field_pos & 3); | |
| if (buf) { | |
| free(db->malloced); | |
| - | db->malloced = buf; |
| - | result = convert_to_struct(db, buf, db->struct_result); |
| + | /* We enlarge buf and move string data up, freeing space |
| + | * for struct passwd/group/spwd at the beginning. This way, |
| + | * entire result of getXXnam is in a single malloced block. |
| + | * This enables easy creation of xmalloc_getpwnam() API. |
| + | */ |
| + | db->malloced = buf = xrealloc(buf, db->size_of + S.string_size); |
| + | memmove(buf + db->size_of, buf, S.string_size); |
| + | result = convert_to_struct(db, buf + db->size_of, buf); |
| } | |
| return result; | |
| } | |