1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
|
From bdd058a0e676d2f013027fcfb2b344c313112a50 Mon Sep 17 00:00:00 2001
From: Qualys Security Advisory <qsa@qualys.com>
Date: Thu, 1 Jan 1970 00:00:00 +0000
Subject: [PATCH 074/126] proc/readproc.c: Fix bugs and overflows in
file2strvec().
Note: this is by far the most important and complex patch of the whole
series, please review it carefully; thank you very much!
For this patch, we decided to keep the original function's design and
skeleton, to avoid regressions and behavior changes, while fixing the
various bugs and overflows. And like the "Harden file2str()" patch, this
patch does not fail when about to overflow, but truncates instead: there
is information available about this process, so return it to the caller;
also, we used INT_MAX as a limit, but a lower limit could be used.
The easy changes:
- Replace sprintf() with snprintf() (and check for truncation).
- Replace "if (n == 0 && rbuf == 0)" with "if (n <= 0 && tot <= 0)" and
do break instead of return: it simplifies the code (only one place to
handle errors), and also guarantees that in the while loop either n or
tot is > 0 (or both), even if n is reset to 0 when about to overflow.
- Remove the "if (n < 0)" block in the while loop: it is (and was) dead
code, since we enter the while loop only if n >= 0.
- Rewrite the missing-null-terminator detection: in the original
function, if the size of the file is a multiple of 2047, a null-
terminator is appended even if the file is already null-terminated.
- Replace "if (n <= 0 && !end_of_file)" with "if (n < 0 || tot <= 0)":
originally, it was equivalent to "if (n < 0)", but we added "tot <= 0"
to handle the first break of the while loop, and to guarantee that in
the rest of the function tot is > 0.
- Double-force ("belt and suspenders") the null-termination of rbuf:
this is (and was) essential to the correctness of the function.
- Replace the final "while" loop with a "for" loop that behaves just
like the preceding "for" loop: in the original function, this would
lead to unexpected results (for example, if rbuf is |\0|A|\0|, this
would return the array {"",NULL} but should return {"","A",NULL}; and
if rbuf is |A|\0|B| (should never happen because rbuf should be null-
terminated), this would make room for two pointers in ret, but would
write three pointers to ret).
The hard changes:
- Prevent the integer overflow of tot in the while loop, but unlike
file2str(), file2strvec() cannot let tot grow until it almost reaches
INT_MAX, because it needs more space for the pointers: this is why we
introduced ARG_LEN, which also guarantees that we can add "align" and
a few sizeof(char*)s to tot without overflowing.
- Prevent the integer overflow of "tot + c + align": when INT_MAX is
(almost) reached, we write the maximal safe amount of pointers to ret
(ARG_LEN guarantees that there is always space for *ret = rbuf and the
NULL terminator).
[carnil: backport for 3.3.9: Add include for limits.h and use of MAX_INT]
CVE: CVE-2018-1124
Upstream-Status: Backport [https://gitlab.com/procps-ng/procps/commit/36c350f07c75aabf747fb833f52a234ae5781b20]
Signed-off-by: Jagadeesh Krishnanjanappa <jkrishnanjanappa@mvista.com>
---
proc/readproc.c | 53 ++++++++++++++++++++++++++++++++---------------------
1 file changed, 32 insertions(+), 21 deletions(-)
diff -Naurp procps-ng-3.3.12_org/proc/readproc.c procps-ng-3.3.12/proc/readproc.c
--- procps-ng-3.3.12_org/proc/readproc.c 2016-07-09 14:49:25.825306872 -0700
+++ procps-ng-3.3.12/proc/readproc.c 2018-07-24 00:46:49.366202531 -0700
@@ -37,6 +37,7 @@
#include <dirent.h>
#include <sys/types.h>
#include <sys/stat.h>
+#include <limits.h>
#ifdef WITH_SYSTEMD
#include <systemd/sd-login.h>
#endif
--- a/proc/readproc.c
+++ b/proc/readproc.c
@@ -600,11 +601,12 @@ static int file2str(const char *director
static char** file2strvec(const char* directory, const char* what) {
char buf[2048]; /* read buf bytes at a time */
- char *p, *rbuf = 0, *endbuf, **q, **ret;
+ char *p, *rbuf = 0, *endbuf, **q, **ret, *strp;
int fd, tot = 0, n, c, end_of_file = 0;
int align;
- sprintf(buf, "%s/%s", directory, what);
+ const int len = snprintf(buf, sizeof buf, "%s/%s", directory, what);
+ if(len <= 0 || (size_t)len >= sizeof buf) return NULL;
fd = open(buf, O_RDONLY, 0);
if(fd==-1) return NULL;
@@ -612,18 +614,23 @@ static char** file2strvec(const char* di
while ((n = read(fd, buf, sizeof buf - 1)) >= 0) {
if (n < (int)(sizeof buf - 1))
end_of_file = 1;
- if (n == 0 && rbuf == 0) {
- close(fd);
- return NULL; /* process died between our open and read */
+ if (n <= 0 && tot <= 0) { /* nothing read now, nothing read before */
+ break; /* process died between our open and read */
}
- if (n < 0) {
- if (rbuf)
- free(rbuf);
- close(fd);
- return NULL; /* read error */
+ /* ARG_LEN is our guesstimated median length of a command-line argument
+ or environment variable (the minimum is 1, the maximum is 131072) */
+ #define ARG_LEN 64
+ if (tot >= INT_MAX / (ARG_LEN + (int)sizeof(char*)) * ARG_LEN - n) {
+ end_of_file = 1; /* integer overflow: null-terminate and break */
+ n = 0; /* but tot > 0 */
}
- if (end_of_file && (n == 0 || buf[n-1]))/* last read char not null */
+ #undef ARG_LEN
+ if (end_of_file &&
+ ((n > 0 && buf[n-1] != '\0') || /* last read char not null */
+ (n <= 0 && rbuf[tot-1] != '\0'))) /* last read char not null */
buf[n++] = '\0'; /* so append null-terminator */
+
+ if (n <= 0) break; /* unneeded (end_of_file = 1) but avoid realloc */
rbuf = xrealloc(rbuf, tot + n); /* allocate more memory */
memcpy(rbuf + tot, buf, n); /* copy buffer into it */
tot += n; /* increment total byte ctr */
@@ -631,29 +638,34 @@ static char** file2strvec(const char* di
break;
}
close(fd);
- if (n <= 0 && !end_of_file) {
+ if (n < 0 || tot <= 0) { /* error, or nothing read */
if (rbuf) free(rbuf);
return NULL; /* read error */
}
+ rbuf[tot-1] = '\0'; /* belt and suspenders (the while loop did it, too) */
endbuf = rbuf + tot; /* count space for pointers */
align = (sizeof(char*)-1) - ((tot + sizeof(char*)-1) & (sizeof(char*)-1));
- for (c = 0, p = rbuf; p < endbuf; p++) {
- if (!*p || *p == '\n')
+ c = sizeof(char*); /* one extra for NULL term */
+ for (p = rbuf; p < endbuf; p++) {
+ if (!*p || *p == '\n') {
+ if (c >= INT_MAX - (tot + (int)sizeof(char*) + align)) break;
c += sizeof(char*);
+ }
if (*p == '\n')
*p = 0;
}
- c += sizeof(char*); /* one extra for NULL term */
rbuf = xrealloc(rbuf, tot + c + align); /* make room for ptrs AT END */
endbuf = rbuf + tot; /* addr just past data buf */
q = ret = (char**) (endbuf+align); /* ==> free(*ret) to dealloc */
- *q++ = p = rbuf; /* point ptrs to the strings */
- endbuf--; /* do not traverse final NUL */
- while (++p < endbuf)
- if (!*p) /* NUL char implies that */
- *q++ = p+1; /* next string -> next char */
-
+ for (strp = p = rbuf; p < endbuf; p++) {
+ if (!*p) { /* NUL char implies that */
+ if (c < 2 * (int)sizeof(char*)) break;
+ c -= sizeof(char*);
+ *q++ = strp; /* point ptrs to the strings */
+ strp = p+1; /* next string -> next char */
+ }
+ }
*q = 0; /* null ptr list terminator */
return ret;
}
|
