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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 real group ID context. |
fca2f191 MJ |
8 | */ |
9 | ||
10 | #define _LGPL_SOURCE | |
9af5d97a | 11 | #include <limits.h> |
b4051ad8 | 12 | #include <stddef.h> |
fca2f191 MJ |
13 | #include <sys/types.h> |
14 | #include <sys/stat.h> | |
15 | #include <unistd.h> | |
16 | #include <lttng/ust-events.h> | |
17 | #include <lttng/ust-tracer.h> | |
0466ac28 | 18 | #include <lttng/ringbuffer-context.h> |
fc80554e MJ |
19 | |
20 | #include "context-internal.h" | |
fca2f191 MJ |
21 | #include "creds.h" |
22 | ||
23 | ||
24 | /* | |
25 | * At the kernel level, user IDs and group IDs are a per-thread attribute. | |
26 | * However, POSIX requires that all threads in a process share the same | |
27 | * credentials. The NPTL threading implementation handles the POSIX | |
28 | * requirements by providing wrapper functions for the various system calls | |
29 | * that change process UIDs and GIDs. These wrapper functions (including those | |
30 | * for setreuid() and setregid()) employ a signal-based technique to ensure | |
31 | * that when one thread changes credentials, all of the other threads in the | |
32 | * process also change their credentials. | |
33 | */ | |
34 | ||
35 | /* | |
36 | * We cache the result to ensure we don't trigger a system call for | |
37 | * each event. User / group IDs are global to the process. | |
38 | */ | |
39 | static gid_t cached_vgid = INVALID_GID; | |
40 | ||
41 | static | |
42 | gid_t get_vgid(void) | |
43 | { | |
44 | gid_t vgid; | |
45 | ||
46 | vgid = CMM_LOAD_SHARED(cached_vgid); | |
47 | ||
48 | if (caa_unlikely(cached_vgid == (gid_t) -1)) { | |
49 | vgid = getgid(); | |
50 | CMM_STORE_SHARED(cached_vgid, vgid); | |
51 | } | |
52 | ||
53 | return vgid; | |
54 | } | |
55 | ||
56 | /* | |
57 | * The vgid can change on setuid, setreuid and setresuid. | |
58 | */ | |
59 | void lttng_context_vgid_reset(void) | |
60 | { | |
61 | CMM_STORE_SHARED(cached_vgid, INVALID_GID); | |
62 | } | |
63 | ||
64 | static | |
daacdbfc | 65 | size_t vgid_get_size(struct lttng_ust_ctx_field *field, size_t offset) |
fca2f191 MJ |
66 | { |
67 | size_t size = 0; | |
68 | ||
dc325c1d | 69 | size += lttng_ust_lib_ring_buffer_align(offset, lttng_ust_rb_alignof(gid_t)); |
fca2f191 MJ |
70 | size += sizeof(gid_t); |
71 | return size; | |
72 | } | |
73 | ||
74 | static | |
daacdbfc | 75 | void vgid_record(struct lttng_ust_ctx_field *field, |
fca2f191 | 76 | struct lttng_ust_lib_ring_buffer_ctx *ctx, |
e7bc0ef6 | 77 | struct lttng_ust_channel_buffer *chan) |
fca2f191 MJ |
78 | { |
79 | gid_t vgid; | |
80 | ||
81 | vgid = get_vgid(); | |
8936b6c0 | 82 | chan->ops->event_write(ctx, &vgid, sizeof(vgid), lttng_ust_rb_alignof(vgid)); |
fca2f191 MJ |
83 | } |
84 | ||
85 | static | |
daacdbfc MD |
86 | void vgid_get_value(struct lttng_ust_ctx_field *field, |
87 | struct lttng_ust_ctx_value *value) | |
fca2f191 MJ |
88 | { |
89 | value->u.s64 = get_vgid(); | |
90 | } | |
91 | ||
daacdbfc | 92 | int lttng_add_vgid_to_ctx(struct lttng_ust_ctx **ctx) |
fca2f191 | 93 | { |
daacdbfc | 94 | struct lttng_ust_ctx_field *field; |
a084756d MD |
95 | struct lttng_ust_type_common *type; |
96 | int ret; | |
97 | ||
98 | type = lttng_ust_create_type_integer(sizeof(gid_t) * CHAR_BIT, | |
dc325c1d | 99 | lttng_ust_rb_alignof(gid_t) * CHAR_BIT, |
eae3c729 | 100 | lttng_ust_is_signed_type(gid_t), |
a084756d MD |
101 | BYTE_ORDER, 10); |
102 | if (!type) | |
fca2f191 | 103 | return -ENOMEM; |
a084756d MD |
104 | field = lttng_append_context(ctx); |
105 | if (!field) { | |
106 | ret = -ENOMEM; | |
107 | goto error_context; | |
108 | } | |
fca2f191 | 109 | if (lttng_find_context(*ctx, "vgid")) { |
a084756d MD |
110 | ret = -EEXIST; |
111 | goto error_find_context; | |
112 | } | |
113 | field->event_field->name = strdup("vgid"); | |
114 | if (!field->event_field->name) { | |
115 | ret = -ENOMEM; | |
116 | goto error_name; | |
fca2f191 | 117 | } |
a084756d | 118 | field->event_field->type = type; |
fca2f191 MJ |
119 | field->get_size = vgid_get_size; |
120 | field->record = vgid_record; | |
121 | field->get_value = vgid_get_value; | |
122 | lttng_context_update(*ctx); | |
123 | return 0; | |
a084756d MD |
124 | |
125 | error_name: | |
126 | error_find_context: | |
127 | lttng_remove_context_field(ctx, field); | |
128 | error_context: | |
129 | lttng_ust_destroy_type(type); | |
130 | return ret; | |
fca2f191 | 131 | } |