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* fileio.c: Fix bugs with large file offsets.

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The previous code assumed that file offsets (off_t values) fit in
EMACS_INT variables, which is not true on typical 32-bit hosts.
The code messed up by falsely reporting buffer overflow in cases
such as (insert-file-contents "big" nil 1 2) into an empty buffer
when "big" contains more than 2**29 bytes, even though this
inserts just one byte and does not overflow the buffer.
(Finsert_file_contents): Store file offsets as off_t
values, not as EMACS_INT values.  Check for overflow when
converting between EMACS_INT and off_t.  When checking for
buffer overflow or for overlap, take the offsets into account.
Don't use EMACS_INT for small values where int suffices.
When checking for overlap, fix a typo: ZV was used where
ZV_BYTE was intended.
(Fwrite_region): Don't assume off_t fits into 'long'.
* buffer.h (struct buffer.modtime_size): Now off_t, not EMACS_INT.
This commit is contained in:
Paul Eggert 2011-09-02 22:23:17 -07:00
parent 9af32a1a25
commit 728f8f0a00
3 changed files with 82 additions and 31 deletions
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19
src/ChangeLog
View File

@ -1,3 +1,22 @@
2011-09-03 Paul Eggert <eggert@cs.ucla.edu>
* fileio.c: Fix bugs with large file offsets.
The previous code assumed that file offsets (off_t values) fit in
EMACS_INT variables, which is not true on typical 32-bit hosts.
The code messed up by falsely reporting buffer overflow in cases
such as (insert-file-contents "big" nil 1 2) into an empty buffer
when "big" contains more than 2**29 bytes, even though this
inserts just one byte and does not overflow the buffer.
(Finsert_file_contents): Store file offsets as off_t
values, not as EMACS_INT values. Check for overflow when
converting between EMACS_INT and off_t. When checking for
buffer overflow or for overlap, take the offsets into account.
Don't use EMACS_INT for small values where int suffices.
When checking for overlap, fix a typo: ZV was used where
ZV_BYTE was intended.
(Fwrite_region): Don't assume off_t fits into 'long'.
* buffer.h (struct buffer.modtime_size): Now off_t, not EMACS_INT.
2011-08-30 Chong Yidong <cyd@stupidchicken.com>
* syntax.c (find_defun_start): Update all cache variables if

2
src/buffer.h
View File

@ -559,7 +559,7 @@ struct buffer
is still the same (since it's rounded up to seconds) but we're actually
not up-to-date. -1 means the size is unknown. Only meaningful if
modtime is actually set. */
EMACS_INT modtime_size;
off_t modtime_size;
/* The value of text->modiff at the last auto-save. */
int auto_save_modified;
/* The value of text->modiff at the last display error.

92
src/fileio.c
View File

@ -3179,6 +3179,7 @@ variable `last-coding-system-used' to the coding system actually used. */)
EMACS_INT inserted = 0;
int nochange = 0;
register EMACS_INT how_much;
off_t beg_offset, end_offset;
register EMACS_INT unprocessed;
int count = SPECPDL_INDEX ();
struct gcpro gcpro1, gcpro2, gcpro3, gcpro4, gcpro5;
@ -3284,15 +3285,6 @@ variable `last-coding-system-used' to the coding system actually used. */)
record_unwind_protect (close_file_unwind, make_number (fd));
/* Check whether the size is too large or negative, which can happen on a
platform that allows file sizes greater than the maximum off_t value. */
if (! not_regular
&& ! (0 <= st.st_size && st.st_size <= BUF_BYTES_MAX))
buffer_overflow ();
/* Prevent redisplay optimizations. */
current_buffer->clip_changed = 1;
if (!NILP (visit))
{
if (!NILP (beg) || !NILP (end))
@ -3302,26 +3294,64 @@ variable `last-coding-system-used' to the coding system actually used. */)
}
if (!NILP (beg))
CHECK_NUMBER (beg);
{
if (! (RANGED_INTEGERP (0, beg, TYPE_MAXIMUM (off_t))))
wrong_type_argument (intern ("file-offset"), beg);
beg_offset = XFASTINT (beg);
}
else
XSETFASTINT (beg, 0);
beg_offset = 0;
if (!NILP (end))
CHECK_NUMBER (end);
{
if (! (RANGED_INTEGERP (0, end, TYPE_MAXIMUM (off_t))))
wrong_type_argument (intern ("file-offset"), end);
end_offset = XFASTINT (end);
}
else
{
if (! not_regular)
if (not_regular)
end_offset = TYPE_MAXIMUM (off_t);
else
{
XSETINT (end, st.st_size);
end_offset = st.st_size;
/* A negative size can happen on a platform that allows file
sizes greater than the maximum off_t value. */
if (end_offset < 0)
buffer_overflow ();
/* The file size returned from stat may be zero, but data
may be readable nonetheless, for example when this is a
file in the /proc filesystem. */
if (st.st_size == 0)
XSETINT (end, READ_BUF_SIZE);
if (end_offset == 0)
end_offset = READ_BUF_SIZE;
}
}
/* Check now whether the buffer will become too large,
in the likely case where the file's length is not changing.
This saves a lot of needless work before a buffer overflow. */
if (! not_regular)
{
/* The likely offset where we will stop reading. We could read
more (or less), if the file grows (or shrinks) as we read it. */
off_t likely_end = min (end_offset, st.st_size);
if (beg_offset < likely_end)
{
ptrdiff_t buf_bytes =
Z_BYTE - (!NILP (replace) ? ZV_BYTE - BEGV_BYTE : 0);
ptrdiff_t buf_growth_max = BUF_BYTES_MAX - buf_bytes;
off_t likely_growth = likely_end - beg_offset;
if (buf_growth_max < likely_growth)
buffer_overflow ();
}
}
/* Prevent redisplay optimizations. */
current_buffer->clip_changed = 1;
if (EQ (Vcoding_system_for_read, Qauto_save_coding))
{
coding_system = coding_inherit_eol_type (Qutf_8_emacs, Qunix);
@ -3465,9 +3495,9 @@ variable `last-coding-system-used' to the coding system actually used. */)
give up on handling REPLACE in the optimized way. */
int giveup_match_end = 0;
if (XINT (beg) != 0)
if (beg_offset != 0)
{
if (emacs_lseek (fd, XINT (beg), SEEK_SET) < 0)
if (lseek (fd, beg_offset, SEEK_SET) < 0)
report_file_error ("Setting file position",
Fcons (orig_filename, Qnil));
}
@ -3515,7 +3545,7 @@ variable `last-coding-system-used' to the coding system actually used. */)
immediate_quit = 0;
/* If the file matches the buffer completely,
there's no need to replace anything. */
if (same_at_start - BEGV_BYTE == XINT (end))
if (same_at_start - BEGV_BYTE == end_offset)
{
emacs_close (fd);
specpdl_ptr--;
@ -3530,16 +3560,17 @@ variable `last-coding-system-used' to the coding system actually used. */)
already found that decoding is necessary, don't waste time. */
while (!giveup_match_end)
{
EMACS_INT total_read, nread, bufpos, curpos, trial;
int total_read, nread, bufpos, trial;
off_t curpos;
/* At what file position are we now scanning? */
curpos = XINT (end) - (ZV_BYTE - same_at_end);
curpos = end_offset - (ZV_BYTE - same_at_end);
/* If the entire file matches the buffer tail, stop the scan. */
if (curpos == 0)
break;
/* How much can we scan in the next step? */
trial = min (curpos, sizeof buffer);
if (emacs_lseek (fd, curpos - trial, SEEK_SET) < 0)
if (lseek (fd, curpos - trial, SEEK_SET) < 0)
report_file_error ("Setting file position",
Fcons (orig_filename, Qnil));
@ -3606,13 +3637,14 @@ variable `last-coding-system-used' to the coding system actually used. */)
/* Don't try to reuse the same piece of text twice. */
overlap = (same_at_start - BEGV_BYTE
- (same_at_end + st.st_size - ZV));
- (same_at_end
+ (! NILP (end) ? end_offset : st.st_size) - ZV_BYTE));
if (overlap > 0)
same_at_end += overlap;
/* Arrange to read only the nonmatching middle part of the file. */
XSETFASTINT (beg, XINT (beg) + (same_at_start - BEGV_BYTE));
XSETFASTINT (end, XINT (end) - (ZV_BYTE - same_at_end));
beg_offset += same_at_start - BEGV_BYTE;
end_offset -= ZV_BYTE - same_at_end;
del_range_byte (same_at_start, same_at_end, 0);
/* Insert from the file at the proper position. */
@ -3657,7 +3689,7 @@ variable `last-coding-system-used' to the coding system actually used. */)
/* First read the whole file, performing code conversion into
CONVERSION_BUFFER. */
if (emacs_lseek (fd, XINT (beg), SEEK_SET) < 0)
if (lseek (fd, beg_offset, SEEK_SET) < 0)
report_file_error ("Setting file position",
Fcons (orig_filename, Qnil));
@ -3824,7 +3856,7 @@ variable `last-coding-system-used' to the coding system actually used. */)
}
if (! not_regular)
total = XINT (end) - XINT (beg);
total = end_offset - beg_offset;
else
/* For a special file, all we can do is guess. */
total = READ_BUF_SIZE;
@ -3845,9 +3877,9 @@ variable `last-coding-system-used' to the coding system actually used. */)
if (GAP_SIZE < total)
make_gap (total - GAP_SIZE);
if (XINT (beg) != 0 || !NILP (replace))
if (beg_offset != 0 || !NILP (replace))
{
if (emacs_lseek (fd, XINT (beg), SEEK_SET) < 0)
if (lseek (fd, beg_offset, SEEK_SET) < 0)
report_file_error ("Setting file position",
Fcons (orig_filename, Qnil));
}
@ -4576,7 +4608,7 @@ This calls `write-region-annotate-functions' at the start, and
if (!NILP (append) && !NILP (Ffile_regular_p (filename)))
{
long ret;
off_t ret;
if (NUMBERP (append))
ret = emacs_lseek (desc, XINT (append), SEEK_CUR);