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Reset next_in and avoid undefined behavior in gzwrite.c #1320

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Reset next_in and avoid undefined behavior in gzwrite.c #1320

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10 changes: 7 additions & 3 deletions gzwrite.c
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Original file line number Diff line number Diff line change
Expand Up @@ -248,6 +248,7 @@ local z_size_t gz_write(gz_statep state, voidpc buf, z_size_t len) {
return state->again ? put - len : 0;
}
} while (len);
state->strm.next_in = state->in;
}

/* input was all buffered or compressed */
Expand Down Expand Up @@ -386,8 +387,11 @@ local int gz_vacate(gz_statep state) {
z_streamp strm;

strm = &(state->strm);
if (strm->next_in == NULL ||
strm->next_in + strm->avail_in <= state->in + state->size)
if (strm->next_in == NULL || strm->avail_in == 0) {
strm->next_in = state->in;
return 0;
}
if (strm->next_in + strm->avail_in <= state->in + state->size)
return 0;
(void)gz_comp(state, Z_NO_FLUSH);
if (strm->avail_in == 0) {
Expand Down Expand Up @@ -454,7 +458,7 @@ int ZEXPORTVA gzvprintf(gzFile file, const char *format, va_list va) {
}
if (strm->avail_in == 0)
strm->next_in = state->in;
next = (char *)(state->in + (strm->next_in - state->in) + strm->avail_in);
next = (char *)(strm->next_in + strm->avail_in);
next[state->size - 1] = 0;
#ifdef NO_vsnprintf
# ifdef HAS_vsprintf_void
Expand Down
20 changes: 20 additions & 0 deletions test/example.c
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Original file line number Diff line number Diff line change
Expand Up @@ -161,6 +161,26 @@ static void test_gzio(const char *fname, Byte *uncompr, uLong uncomprLen) {
}

gzclose(file);

/* Test large buffer gzwrite followed immediately by gzprintf */
file = gzopen(fname, "wb");
if (file == NULL) {
fprintf(stderr, "gzopen error\n");
exit(1);
}
{
char large_buf[16384];
memset(large_buf, 'A', sizeof(large_buf));
if (gzwrite(file, large_buf, (unsigned)sizeof(large_buf)) != (int)sizeof(large_buf)) {
fprintf(stderr, "gzwrite err: %s\n", gzerror(file, &err));
exit(1);
}
}
if (gzprintf(file, "%s", "test") != 4) {
fprintf(stderr, "gzprintf after large gzwrite err: %s\n", gzerror(file, &err));
exit(1);
}
gzclose(file);
#endif
}

Expand Down