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fca2f191 | 1 | /* |
c0c0989a | 2 | * SPDX-License-Identifier: LGPL-2.1-only |
fca2f191 MJ |
3 | * |
4 | * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
c0c0989a | 5 | * Copyright (C) 2019 Michael Jeanson <mjeanson@efficios.com> |
fca2f191 | 6 | * |
c0c0989a | 7 | * LTTng UST namespaced saved set-user ID context. |
fca2f191 MJ |
8 | */ |
9 | ||
fca2f191 | 10 | #define _LGPL_SOURCE |
b4051ad8 | 11 | #include <stddef.h> |
fca2f191 MJ |
12 | #include <sys/types.h> |
13 | #include <sys/stat.h> | |
14 | #include <unistd.h> | |
15 | #include <lttng/ust-events.h> | |
16 | #include <lttng/ust-tracer.h> | |
0466ac28 | 17 | #include <lttng/ringbuffer-context.h> |
fc80554e MJ |
18 | |
19 | #include "context-internal.h" | |
fca2f191 MJ |
20 | #include "creds.h" |
21 | ||
22 | ||
23 | /* | |
24 | * At the kernel level, user IDs and group IDs are a per-thread attribute. | |
25 | * However, POSIX requires that all threads in a process share the same | |
26 | * credentials. The NPTL threading implementation handles the POSIX | |
27 | * requirements by providing wrapper functions for the various system calls | |
28 | * that change process UIDs and GIDs. These wrapper functions (including those | |
29 | * for setreuid() and setregid()) employ a signal-based technique to ensure | |
30 | * that when one thread changes credentials, all of the other threads in the | |
31 | * process also change their credentials. | |
32 | */ | |
33 | ||
34 | /* | |
35 | * We cache the result to ensure we don't trigger a system call for | |
36 | * each event. User / group IDs are global to the process. | |
37 | */ | |
38 | static uid_t cached_vsuid = INVALID_UID; | |
39 | ||
40 | static | |
41 | uid_t get_vsuid(void) | |
42 | { | |
43 | uid_t vsuid; | |
44 | ||
45 | vsuid = CMM_LOAD_SHARED(cached_vsuid); | |
46 | ||
47 | if (caa_unlikely(vsuid == INVALID_UID)) { | |
48 | uid_t uid, euid, suid; | |
49 | ||
50 | if (getresuid(&uid, &euid, &suid) == 0) { | |
51 | vsuid = suid; | |
52 | CMM_STORE_SHARED(cached_vsuid, vsuid); | |
53 | } | |
54 | } | |
55 | ||
56 | return vsuid; | |
57 | } | |
58 | ||
59 | /* | |
60 | * The vsuid can change on setuid, setreuid and setresuid. | |
61 | */ | |
62 | void lttng_context_vsuid_reset(void) | |
63 | { | |
64 | CMM_STORE_SHARED(cached_vsuid, INVALID_UID); | |
65 | } | |
66 | ||
67 | static | |
daacdbfc | 68 | size_t vsuid_get_size(struct lttng_ust_ctx_field *field, size_t offset) |
fca2f191 MJ |
69 | { |
70 | size_t size = 0; | |
71 | ||
72 | size += lib_ring_buffer_align(offset, lttng_alignof(uid_t)); | |
73 | size += sizeof(uid_t); | |
74 | return size; | |
75 | } | |
76 | ||
77 | static | |
daacdbfc | 78 | void vsuid_record(struct lttng_ust_ctx_field *field, |
fca2f191 MJ |
79 | struct lttng_ust_lib_ring_buffer_ctx *ctx, |
80 | struct lttng_channel *chan) | |
81 | { | |
82 | uid_t vsuid; | |
83 | ||
84 | vsuid = get_vsuid(); | |
85 | lib_ring_buffer_align_ctx(ctx, lttng_alignof(vsuid)); | |
86 | chan->ops->event_write(ctx, &vsuid, sizeof(vsuid)); | |
87 | } | |
88 | ||
89 | static | |
daacdbfc MD |
90 | void vsuid_get_value(struct lttng_ust_ctx_field *field, |
91 | struct lttng_ust_ctx_value *value) | |
fca2f191 MJ |
92 | { |
93 | value->u.s64 = get_vsuid(); | |
94 | } | |
95 | ||
daacdbfc | 96 | int lttng_add_vsuid_to_ctx(struct lttng_ust_ctx **ctx) |
fca2f191 | 97 | { |
daacdbfc | 98 | struct lttng_ust_ctx_field *field; |
a084756d MD |
99 | struct lttng_ust_type_common *type; |
100 | int ret; | |
101 | ||
102 | type = lttng_ust_create_type_integer(sizeof(uid_t) * CHAR_BIT, | |
103 | lttng_alignof(uid_t) * CHAR_BIT, | |
104 | lttng_is_signed_type(uid_t), | |
105 | BYTE_ORDER, 10); | |
106 | if (!type) | |
fca2f191 | 107 | return -ENOMEM; |
a084756d MD |
108 | field = lttng_append_context(ctx); |
109 | if (!field) { | |
110 | ret = -ENOMEM; | |
111 | goto error_context; | |
112 | } | |
fca2f191 | 113 | if (lttng_find_context(*ctx, "vsuid")) { |
a084756d MD |
114 | ret = -EEXIST; |
115 | goto error_find_context; | |
116 | } | |
117 | field->event_field->name = strdup("vsuid"); | |
118 | if (!field->event_field->name) { | |
119 | ret = -ENOMEM; | |
120 | goto error_name; | |
fca2f191 | 121 | } |
a084756d | 122 | field->event_field->type = type; |
fca2f191 MJ |
123 | field->get_size = vsuid_get_size; |
124 | field->record = vsuid_record; | |
125 | field->get_value = vsuid_get_value; | |
126 | lttng_context_update(*ctx); | |
127 | return 0; | |
a084756d MD |
128 | |
129 | error_name: | |
130 | error_find_context: | |
131 | lttng_remove_context_field(ctx, field); | |
132 | error_context: | |
133 | lttng_ust_destroy_type(type); | |
134 | return ret; | |
fca2f191 | 135 | } |