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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> | |
17 | #include <lttng/ringbuffer-config.h> | |
18 | #include "creds.h" | |
19 | ||
20 | ||
21 | /* | |
22 | * At the kernel level, user IDs and group IDs are a per-thread attribute. | |
23 | * However, POSIX requires that all threads in a process share the same | |
24 | * credentials. The NPTL threading implementation handles the POSIX | |
25 | * requirements by providing wrapper functions for the various system calls | |
26 | * that change process UIDs and GIDs. These wrapper functions (including those | |
27 | * for setreuid() and setregid()) employ a signal-based technique to ensure | |
28 | * that when one thread changes credentials, all of the other threads in the | |
29 | * process also change their credentials. | |
30 | */ | |
31 | ||
32 | /* | |
33 | * We cache the result to ensure we don't trigger a system call for | |
34 | * each event. User / group IDs are global to the process. | |
35 | */ | |
36 | static uid_t cached_vsuid = INVALID_UID; | |
37 | ||
38 | static | |
39 | uid_t get_vsuid(void) | |
40 | { | |
41 | uid_t vsuid; | |
42 | ||
43 | vsuid = CMM_LOAD_SHARED(cached_vsuid); | |
44 | ||
45 | if (caa_unlikely(vsuid == INVALID_UID)) { | |
46 | uid_t uid, euid, suid; | |
47 | ||
48 | if (getresuid(&uid, &euid, &suid) == 0) { | |
49 | vsuid = suid; | |
50 | CMM_STORE_SHARED(cached_vsuid, vsuid); | |
51 | } | |
52 | } | |
53 | ||
54 | return vsuid; | |
55 | } | |
56 | ||
57 | /* | |
58 | * The vsuid can change on setuid, setreuid and setresuid. | |
59 | */ | |
60 | void lttng_context_vsuid_reset(void) | |
61 | { | |
62 | CMM_STORE_SHARED(cached_vsuid, INVALID_UID); | |
63 | } | |
64 | ||
65 | static | |
66 | size_t vsuid_get_size(struct lttng_ctx_field *field, size_t offset) | |
67 | { | |
68 | size_t size = 0; | |
69 | ||
70 | size += lib_ring_buffer_align(offset, lttng_alignof(uid_t)); | |
71 | size += sizeof(uid_t); | |
72 | return size; | |
73 | } | |
74 | ||
75 | static | |
76 | void vsuid_record(struct lttng_ctx_field *field, | |
77 | struct lttng_ust_lib_ring_buffer_ctx *ctx, | |
78 | struct lttng_channel *chan) | |
79 | { | |
80 | uid_t vsuid; | |
81 | ||
82 | vsuid = get_vsuid(); | |
83 | lib_ring_buffer_align_ctx(ctx, lttng_alignof(vsuid)); | |
84 | chan->ops->event_write(ctx, &vsuid, sizeof(vsuid)); | |
85 | } | |
86 | ||
87 | static | |
88 | void vsuid_get_value(struct lttng_ctx_field *field, | |
89 | struct lttng_ctx_value *value) | |
90 | { | |
91 | value->u.s64 = get_vsuid(); | |
92 | } | |
93 | ||
94 | int lttng_add_vsuid_to_ctx(struct lttng_ctx **ctx) | |
95 | { | |
96 | struct lttng_ctx_field *field; | |
97 | ||
98 | field = lttng_append_context(ctx); | |
99 | if (!field) | |
100 | return -ENOMEM; | |
101 | if (lttng_find_context(*ctx, "vsuid")) { | |
102 | lttng_remove_context_field(ctx, field); | |
103 | return -EEXIST; | |
104 | } | |
105 | field->event_field.name = "vsuid"; | |
106 | field->event_field.type.atype = atype_integer; | |
218deb69 MD |
107 | field->event_field.type.u.integer.size = sizeof(uid_t) * CHAR_BIT; |
108 | field->event_field.type.u.integer.alignment = lttng_alignof(uid_t) * CHAR_BIT; | |
109 | field->event_field.type.u.integer.signedness = lttng_is_signed_type(uid_t); | |
110 | field->event_field.type.u.integer.reverse_byte_order = 0; | |
111 | field->event_field.type.u.integer.base = 10; | |
112 | field->event_field.type.u.integer.encoding = lttng_encode_none; | |
fca2f191 MJ |
113 | field->get_size = vsuid_get_size; |
114 | field->record = vsuid_record; | |
115 | field->get_value = vsuid_get_value; | |
116 | lttng_context_update(*ctx); | |
117 | return 0; | |
118 | } |