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Improve buffer-overflow checking.

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* fileio.c (Finsert_file_contents):
* insdel.c (insert_from_buffer_1, replace_range, replace_range_2):
Remove the old (too-loose) buffer overflow checks.
They weren't needed, since make_gap checks for buffer overflow.
* insdel.c (make_gap_larger): Catch buffer overflows that were missed.
The old code merely checked for Emacs fixnum overflow, and relied
on undefined (wraparound) behavior.  The new code avoids undefined
behavior, and also checks for ptrdiff_t and/or size_t overflow.
This commit is contained in:
Paul Eggert 2011-06-16 14:18:12 -07:00
parent 21d890a4ec
commit 1c8e352f7e
3 changed files with 19 additions and 36 deletions
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10
src/ChangeLog
View file

@ -1,5 +1,15 @@
2011-06-16 Paul Eggert <eggert@cs.ucla.edu>
Improve buffer-overflow checking.
* fileio.c (Finsert_file_contents):
* insdel.c (insert_from_buffer_1, replace_range, replace_range_2):
Remove the old (too-loose) buffer overflow checks.
They weren't needed, since make_gap checks for buffer overflow.
* insdel.c (make_gap_larger): Catch buffer overflows that were missed.
The old code merely checked for Emacs fixnum overflow, and relied
on undefined (wraparound) behavior. The new code avoids undefined
behavior, and also checks for ptrdiff_t and/or size_t overflow.
* editfns.c (Finsert_char): Don't dump core with very negative counts.
Tune. Don't use wider integers than needed. Don't use alloca.
Use a bigger 'string' buffer. Rewrite to avoid 'n > 0' test.

11
src/fileio.c
View file

@ -3800,16 +3800,7 @@ variable `last-coding-system-used' to the coding system actually used. */)
}
if (! not_regular)
{
register Lisp_Object temp;
total = XINT (end) - XINT (beg);
/* Make sure point-max won't overflow after this insertion. */
XSETINT (temp, total);
if (total != XINT (temp))
buffer_overflow ();
}
total = XINT (end) - XINT (beg);
else
/* For a special file, all we can do is guess. */
total = READ_BUF_SIZE;

34
src/insdel.c
View file

@ -406,16 +406,16 @@ make_gap_larger (EMACS_INT nbytes_added)
EMACS_INT real_gap_loc;
EMACS_INT real_gap_loc_byte;
EMACS_INT old_gap_size;
EMACS_INT current_size = Z_BYTE - BEG_BYTE + GAP_SIZE;
enum { enough_for_a_while = 2000 };
/* If we have to get more space, get enough to last a while. */
nbytes_added += 2000;
if (BUF_BYTES_MAX - current_size < nbytes_added)
buffer_overflow ();
{ EMACS_INT total_size = Z_BYTE - BEG_BYTE + GAP_SIZE + nbytes_added;
if (total_size < 0
/* Don't allow a buffer size that won't fit in a Lisp integer. */
|| total_size != XINT (make_number (total_size)))
buffer_overflow ();
}
/* If we have to get more space, get enough to last a while;
but do not exceed the maximum buffer size. */
nbytes_added = min (nbytes_added + enough_for_a_while,
BUF_BYTES_MAX - current_size);
enlarge_buffer_text (current_buffer, nbytes_added);
@ -1069,7 +1069,6 @@ static void
insert_from_buffer_1 (struct buffer *buf,
EMACS_INT from, EMACS_INT nchars, int inherit)
{
register Lisp_Object temp;
EMACS_INT chunk, chunk_expanded;
EMACS_INT from_byte = buf_charpos_to_bytepos (buf, from);
EMACS_INT to_byte = buf_charpos_to_bytepos (buf, from + nchars);
@ -1108,11 +1107,6 @@ insert_from_buffer_1 (struct buffer *buf,
outgoing_nbytes = outgoing_before_gap + outgoing_after_gap;
}
/* Make sure point-max won't overflow after this insertion. */
XSETINT (temp, outgoing_nbytes + Z);
if (outgoing_nbytes + Z != XINT (temp))
buffer_overflow ();
/* Do this before moving and increasing the gap,
because the before-change hooks might move the gap
or make it smaller. */
@ -1309,7 +1303,6 @@ replace_range (EMACS_INT from, EMACS_INT to, Lisp_Object new,
EMACS_INT insbytes = SBYTES (new);
EMACS_INT from_byte, to_byte;
EMACS_INT nbytes_del, nchars_del;
register Lisp_Object temp;
struct gcpro gcpro1;
INTERVAL intervals;
EMACS_INT outgoing_insbytes = insbytes;
@ -1353,11 +1346,6 @@ replace_range (EMACS_INT from, EMACS_INT to, Lisp_Object new,
outgoing_insbytes
= count_size_as_multibyte (SDATA (new), insbytes);
/* Make sure point-max won't overflow after this insertion. */
XSETINT (temp, Z_BYTE - nbytes_del + outgoing_insbytes);
if (Z_BYTE - nbytes_del + outgoing_insbytes != XINT (temp))
buffer_overflow ();
GCPRO1 (new);
/* Make sure the gap is somewhere in or next to what we are deleting. */
@ -1488,7 +1476,6 @@ replace_range_2 (EMACS_INT from, EMACS_INT from_byte,
int markers)
{
EMACS_INT nbytes_del, nchars_del;
Lisp_Object temp;
CHECK_MARKERS ();
@ -1498,11 +1485,6 @@ replace_range_2 (EMACS_INT from, EMACS_INT from_byte,
if (nbytes_del <= 0 && insbytes == 0)
return;
/* Make sure point-max won't overflow after this insertion. */
XSETINT (temp, Z_BYTE - nbytes_del + insbytes);
if (Z_BYTE - nbytes_del + insbytes != XINT (temp))
buffer_overflow ();
/* Make sure the gap is somewhere in or next to what we are deleting. */
if (from > GPT)
gap_right (from, from_byte);