Mercurial > hg > mercurial-source
annotate mercurial/mpatch.c @ 38976:1ec4cb8cbc87 stable
mpatch: introduce a safeadd() helper to work around UB int overflow
We're about to make extensive use of this. This change duplicates some
stdbool.h portability hacks from cext/util.h. We should probably clean
that up in the future, but we'll skip that for now in order to make
security backports easier.
| author | Augie Fackler <augie@google.com> |
|---|---|
| date | Mon, 30 Apr 2018 22:13:42 -0400 |
| parents | faa924469635 |
| children | b8b253aec953 |
| rev | line source |
|---|---|
| 72 | 1 /* |
| 2 mpatch.c - efficient binary patching for Mercurial | |
| 3 | |
| 4 This implements a patch algorithm that's O(m + nlog n) where m is the | |
| 5 size of the output and n is the number of patches. | |
| 6 | |
| 7 Given a list of binary patches, it unpacks each into a hunk list, | |
| 8 then combines the hunk lists with a treewise recursion to form a | |
| 9 single hunk list. This hunk list is then applied to the original | |
| 10 text. | |
| 11 | |
| 12 The text (or binary) fragments are copied directly from their source | |
| 13 Python objects into a preallocated output string to avoid the | |
| 14 allocation of intermediate Python objects. Working memory is about 2x | |
| 15 the total number of hunks. | |
| 16 | |
| 2858 | 17 Copyright 2005, 2006 Matt Mackall <mpm@selenic.com> |
| 72 | 18 |
| 19 This software may be used and distributed according to the terms | |
| 20 of the GNU General Public License, incorporated herein by reference. | |
| 21 */ | |
| 22 | |
|
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23 #include <limits.h> |
| 72 | 24 #include <stdlib.h> |
| 25 #include <string.h> | |
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26 |
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27 #include "bitmanipulation.h" |
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28 #include "compat.h" |
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29 #include "mpatch.h" |
| 72 | 30 |
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31 /* VC9 doesn't include bool and lacks stdbool.h based on cext/util.h */ |
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32 #if defined(_MSC_VER) || __STDC_VERSION__ < 199901L |
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33 #define true 1 |
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34 #define false 0 |
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35 typedef unsigned char bool; |
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36 #else |
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37 #include <stdbool.h> |
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38 #endif |
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39 |
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40 static struct mpatch_flist *lalloc(ssize_t size) |
| 72 | 41 { |
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42 struct mpatch_flist *a = NULL; |
| 72 | 43 |
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44 if (size < 1) |
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45 size = 1; |
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46 |
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47 a = (struct mpatch_flist *)malloc(sizeof(struct mpatch_flist)); |
| 128 | 48 if (a) { |
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49 a->base = (struct mpatch_frag *)malloc( |
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50 sizeof(struct mpatch_frag) * size); |
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51 if (a->base) { |
| 128 | 52 a->head = a->tail = a->base; |
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53 return a; |
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54 } |
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55 free(a); |
| 128 | 56 } |
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57 return NULL; |
| 72 | 58 } |
| 59 | |
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60 void mpatch_lfree(struct mpatch_flist *a) |
| 72 | 61 { |
| 128 | 62 if (a) { |
| 63 free(a->base); | |
| 64 free(a); | |
| 65 } | |
| 72 | 66 } |
| 67 | |
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68 static ssize_t lsize(struct mpatch_flist *a) |
| 72 | 69 { |
| 70 return a->tail - a->head; | |
| 71 } | |
| 72 | |
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73 /* add helper to add src and *dest iff it won't overflow */ |
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74 static inline bool safeadd(int src, int *dest) |
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75 { |
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76 if ((src > 0) == (*dest > 0)) { |
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77 if (*dest > 0) { |
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78 if (src > (INT_MAX - *dest)) { |
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79 return false; |
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80 } |
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81 } else { |
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82 if (src < (INT_MIN - *dest)) { |
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83 return false; |
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84 } |
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85 } |
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86 } |
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87 *dest += src; |
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88 return true; |
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89 } |
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90 |
| 72 | 91 /* move hunks in source that are less cut to dest, compensating |
| 92 for changes in offset. the last hunk may be split if necessary. | |
| 93 */ | |
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94 static int gather(struct mpatch_flist *dest, struct mpatch_flist *src, int cut, |
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95 int offset) |
| 72 | 96 { |
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97 struct mpatch_frag *d = dest->tail, *s = src->head; |
| 72 | 98 int postend, c, l; |
| 99 | |
| 100 while (s != src->tail) { | |
| 101 if (s->start + offset >= cut) | |
| 82 | 102 break; /* we've gone far enough */ |
| 72 | 103 |
| 104 postend = offset + s->start + s->len; | |
| 105 if (postend <= cut) { | |
| 106 /* save this hunk */ | |
| 107 offset += s->start + s->len - s->end; | |
| 108 *d++ = *s++; | |
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109 } else { |
| 72 | 110 /* break up this hunk */ |
| 111 c = cut - offset; | |
| 112 if (s->end < c) | |
| 113 c = s->end; | |
| 114 l = cut - offset - s->start; | |
| 115 if (s->len < l) | |
| 116 l = s->len; | |
| 117 | |
| 118 offset += s->start + l - c; | |
| 119 | |
| 120 d->start = s->start; | |
| 121 d->end = c; | |
| 122 d->len = l; | |
| 123 d->data = s->data; | |
| 124 d++; | |
| 125 s->start = c; | |
| 126 s->len = s->len - l; | |
| 127 s->data = s->data + l; | |
| 128 | |
| 82 | 129 break; |
| 72 | 130 } |
| 131 } | |
| 132 | |
| 133 dest->tail = d; | |
| 134 src->head = s; | |
| 135 return offset; | |
| 136 } | |
| 137 | |
| 138 /* like gather, but with no output list */ | |
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139 static int discard(struct mpatch_flist *src, int cut, int offset) |
| 72 | 140 { |
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141 struct mpatch_frag *s = src->head; |
| 72 | 142 int postend, c, l; |
| 143 | |
| 144 while (s != src->tail) { | |
| 145 if (s->start + offset >= cut) | |
| 82 | 146 break; |
| 72 | 147 |
| 148 postend = offset + s->start + s->len; | |
| 149 if (postend <= cut) { | |
| 150 offset += s->start + s->len - s->end; | |
| 151 s++; | |
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152 } else { |
| 72 | 153 c = cut - offset; |
| 154 if (s->end < c) | |
| 155 c = s->end; | |
| 156 l = cut - offset - s->start; | |
| 157 if (s->len < l) | |
| 158 l = s->len; | |
| 159 | |
| 160 offset += s->start + l - c; | |
| 161 s->start = c; | |
| 162 s->len = s->len - l; | |
| 163 s->data = s->data + l; | |
| 164 | |
| 82 | 165 break; |
| 72 | 166 } |
| 167 } | |
| 168 | |
| 169 src->head = s; | |
| 170 return offset; | |
| 171 } | |
| 172 | |
| 173 /* combine hunk lists a and b, while adjusting b for offset changes in a/ | |
| 174 this deletes a and b and returns the resultant list. */ | |
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175 static struct mpatch_flist *combine(struct mpatch_flist *a, |
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176 struct mpatch_flist *b) |
| 72 | 177 { |
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178 struct mpatch_flist *c = NULL; |
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179 struct mpatch_frag *bh, *ct; |
| 72 | 180 int offset = 0, post; |
| 181 | |
| 128 | 182 if (a && b) |
| 183 c = lalloc((lsize(a) + lsize(b)) * 2); | |
| 184 | |
| 185 if (c) { | |
| 72 | 186 |
| 128 | 187 for (bh = b->head; bh != b->tail; bh++) { |
| 188 /* save old hunks */ | |
| 189 offset = gather(c, a, bh->start, offset); | |
| 72 | 190 |
| 128 | 191 /* discard replaced hunks */ |
| 192 post = discard(a, bh->end, offset); | |
| 72 | 193 |
| 128 | 194 /* insert new hunk */ |
| 195 ct = c->tail; | |
| 196 ct->start = bh->start - offset; | |
| 197 ct->end = bh->end - post; | |
| 198 ct->len = bh->len; | |
| 199 ct->data = bh->data; | |
| 200 c->tail++; | |
| 201 offset = post; | |
| 202 } | |
| 203 | |
| 204 /* hold on to tail from a */ | |
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205 memcpy(c->tail, a->head, sizeof(struct mpatch_frag) * lsize(a)); |
| 128 | 206 c->tail += lsize(a); |
| 72 | 207 } |
| 208 | |
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209 mpatch_lfree(a); |
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210 mpatch_lfree(b); |
| 72 | 211 return c; |
| 212 } | |
| 213 | |
| 214 /* decode a binary patch into a hunk list */ | |
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215 int mpatch_decode(const char *bin, ssize_t len, struct mpatch_flist **res) |
| 72 | 216 { |
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217 struct mpatch_flist *l; |
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218 struct mpatch_frag *lt; |
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219 int pos = 0; |
| 72 | 220 |
| 221 /* assume worst case size, we won't have many of these lists */ | |
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222 l = lalloc(len / 12 + 1); |
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223 if (!l) |
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224 return MPATCH_ERR_NO_MEM; |
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225 |
| 72 | 226 lt = l->tail; |
| 227 | |
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228 /* We check against len-11 to ensure we have at least 12 bytes |
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229 left in the patch so we can read our three be32s out of it. */ |
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230 while (pos >= 0 && pos < (len - 11)) { |
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231 lt->start = getbe32(bin + pos); |
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232 lt->end = getbe32(bin + pos + 4); |
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233 lt->len = getbe32(bin + pos + 8); |
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234 lt->data = bin + pos + 12; |
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235 pos += 12 + lt->len; |
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236 if (lt->start > lt->end || lt->len < 0) |
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237 break; /* sanity check */ |
| 72 | 238 lt++; |
| 239 } | |
| 240 | |
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241 if (pos != len) { |
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242 mpatch_lfree(l); |
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243 return MPATCH_ERR_CANNOT_BE_DECODED; |
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244 } |
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245 |
| 72 | 246 l->tail = lt; |
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247 *res = l; |
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248 return 0; |
| 72 | 249 } |
| 250 | |
| 251 /* calculate the size of resultant text */ | |
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252 ssize_t mpatch_calcsize(ssize_t len, struct mpatch_flist *l) |
| 72 | 253 { |
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254 ssize_t outlen = 0, last = 0; |
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255 struct mpatch_frag *f = l->head; |
| 72 | 256 |
| 257 while (f != l->tail) { | |
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258 if (f->start < last || f->end > len) { |
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259 return MPATCH_ERR_INVALID_PATCH; |
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260 } |
| 72 | 261 outlen += f->start - last; |
| 262 last = f->end; | |
| 263 outlen += f->len; | |
| 264 f++; | |
| 265 } | |
| 266 | |
| 267 outlen += len - last; | |
| 268 return outlen; | |
| 269 } | |
| 270 | |
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271 int mpatch_apply(char *buf, const char *orig, ssize_t len, |
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272 struct mpatch_flist *l) |
| 72 | 273 { |
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274 struct mpatch_frag *f = l->head; |
| 72 | 275 int last = 0; |
| 276 char *p = buf; | |
| 277 | |
| 278 while (f != l->tail) { | |
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279 if (f->start < last || f->start > len || f->end > len || |
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280 last < 0) { |
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281 return MPATCH_ERR_INVALID_PATCH; |
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282 } |
| 72 | 283 memcpy(p, orig + last, f->start - last); |
| 284 p += f->start - last; | |
| 285 memcpy(p, f->data, f->len); | |
| 286 last = f->end; | |
| 287 p += f->len; | |
| 288 f++; | |
| 289 } | |
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290 if (last < 0) { |
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291 return MPATCH_ERR_INVALID_PATCH; |
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292 } |
| 72 | 293 memcpy(p, orig + last, len - last); |
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294 return 0; |
| 72 | 295 } |
| 296 | |
| 297 /* recursively generate a patch of all bins between start and end */ | |
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298 struct mpatch_flist * |
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299 mpatch_fold(void *bins, struct mpatch_flist *(*get_next_item)(void *, ssize_t), |
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300 ssize_t start, ssize_t end) |
| 72 | 301 { |
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302 ssize_t len; |
| 72 | 303 |
| 304 if (start + 1 == end) { | |
| 305 /* trivial case, output a decoded list */ | |
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306 return get_next_item(bins, start); |
| 72 | 307 } |
| 308 | |
| 309 /* divide and conquer, memory management is elsewhere */ | |
| 310 len = (end - start) / 2; | |
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311 return combine(mpatch_fold(bins, get_next_item, start, start + len), |
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312 mpatch_fold(bins, get_next_item, start + len, end)); |
| 72 | 313 } |