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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 |
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> | |
0b4b8811 | 18 | #include <lttng/ust-ringbuffer-context.h> |
fc80554e MJ |
19 | |
20 | #include "context-internal.h" | |
6abdf6dc | 21 | #include "common/creds.h" |
fca2f191 MJ |
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 uid_t cached_vsuid = INVALID_UID; | |
40 | ||
41 | static | |
42 | uid_t get_vsuid(void) | |
43 | { | |
44 | uid_t vsuid; | |
45 | ||
46 | vsuid = CMM_LOAD_SHARED(cached_vsuid); | |
47 | ||
48 | if (caa_unlikely(vsuid == INVALID_UID)) { | |
49 | uid_t uid, euid, suid; | |
50 | ||
51 | if (getresuid(&uid, &euid, &suid) == 0) { | |
52 | vsuid = suid; | |
53 | CMM_STORE_SHARED(cached_vsuid, vsuid); | |
54 | } | |
55 | } | |
56 | ||
57 | return vsuid; | |
58 | } | |
59 | ||
60 | /* | |
61 | * The vsuid can change on setuid, setreuid and setresuid. | |
62 | */ | |
63 | void lttng_context_vsuid_reset(void) | |
64 | { | |
65 | CMM_STORE_SHARED(cached_vsuid, INVALID_UID); | |
66 | } | |
67 | ||
68 | static | |
4e48b5d2 | 69 | size_t vsuid_get_size(void *priv __attribute__((unused)), |
2208d8b5 | 70 | size_t offset) |
fca2f191 MJ |
71 | { |
72 | size_t size = 0; | |
73 | ||
b5457df5 | 74 | size += lttng_ust_ring_buffer_align(offset, lttng_ust_rb_alignof(uid_t)); |
fca2f191 MJ |
75 | size += sizeof(uid_t); |
76 | return size; | |
77 | } | |
78 | ||
79 | static | |
4e48b5d2 | 80 | void vsuid_record(void *priv __attribute__((unused)), |
b5457df5 | 81 | struct lttng_ust_ring_buffer_ctx *ctx, |
e7bc0ef6 | 82 | struct lttng_ust_channel_buffer *chan) |
fca2f191 MJ |
83 | { |
84 | uid_t vsuid; | |
85 | ||
86 | vsuid = get_vsuid(); | |
8936b6c0 | 87 | chan->ops->event_write(ctx, &vsuid, sizeof(vsuid), lttng_ust_rb_alignof(vsuid)); |
fca2f191 MJ |
88 | } |
89 | ||
90 | static | |
4e48b5d2 | 91 | void vsuid_get_value(void *priv __attribute__((unused)), |
daacdbfc | 92 | struct lttng_ust_ctx_value *value) |
fca2f191 MJ |
93 | { |
94 | value->u.s64 = get_vsuid(); | |
95 | } | |
96 | ||
4e48b5d2 MD |
97 | static const struct lttng_ust_ctx_field *ctx_field = lttng_ust_static_ctx_field( |
98 | lttng_ust_static_event_field("vsuid", | |
99 | lttng_ust_static_type_integer(sizeof(uid_t) * CHAR_BIT, | |
100 | lttng_ust_rb_alignof(uid_t) * CHAR_BIT, | |
101 | lttng_ust_is_signed_type(uid_t), | |
102 | BYTE_ORDER, 10), | |
103 | false, false), | |
104 | vsuid_get_size, | |
105 | vsuid_record, | |
106 | vsuid_get_value, | |
107 | NULL, NULL); | |
108 | ||
daacdbfc | 109 | int lttng_add_vsuid_to_ctx(struct lttng_ust_ctx **ctx) |
fca2f191 | 110 | { |
a084756d MD |
111 | int ret; |
112 | ||
4e48b5d2 | 113 | if (lttng_find_context(*ctx, ctx_field->event_field->name)) { |
a084756d MD |
114 | ret = -EEXIST; |
115 | goto error_find_context; | |
116 | } | |
4e48b5d2 MD |
117 | ret = lttng_ust_context_append(ctx, ctx_field); |
118 | if (ret) | |
119 | return ret; | |
fca2f191 | 120 | return 0; |
a084756d | 121 | |
a084756d | 122 | error_find_context: |
a084756d | 123 | return ret; |
fca2f191 | 124 | } |