You're right. Maybe I should read up on my less. :-)
OK martijn@ for the full diff.
On 08/02/17 19:55, Anton Lindqvist wrote:
> On Wed, Aug 02, 2017 at 07:19:50PM +0200, Martijn van Duren wrote:
>> OK martijn@ for the pattern.c part.
>>
>> The search.c part seems unneeded.
>> - If we don't have a match we don't enter hilite_line at all.
>> - If we have a match and don't negate get sp/ep for every match.
>> - If we have a match and negate, with your process.c patch we get a
>> sp/ep with value NULL and return before entering the do/while.
>>
>> So with the above there's no situation where we can get in the
>> do/while loop and still need to check for NULL on every pass, and the
>> move is thus unnecessary churn.
>
> The changes to pattern.c do solve the initial problem as reported by
> Larry. However, I'm experiencing a crash if I remove the changes to
> search.c:
>
> $ cat in
> foo
> bar
> bar
> $ less in # type: /!foo<CR>
>
>>
>> On 07/28/17 13:32, Anton Lindqvist wrote:
>>> On Fri, Jul 28, 2017 at 01:19:39PM +0200, Theo Buehler wrote:
>>>> On Thu, Jul 27, 2017 at 10:31:51AM +0100, Larry Hynes wrote:
>>>>> Hi
>>>>>
>>>>> $ env | grep LESS
>>>>> LESSHISTFILE=-
>>>>> LESS="-i -M -R -g -c"
>>>>> LESSCHARSET=utf-8
>>>>>
>>>>> $ unset LESS
>>>>> $ unset LESSCHARSET
>>>>> $ unset LESSHISTFILE
>>>>>
>>>>> $ LESS="-g"
>>>>> $ echo 'foo\nbar\nfoo\nbar\nfoo\nbar' | less
>>>>>
>>>>> While in less, '/' to search, then '^N', or '!', to search for lines
>>>>> which do NOT match the pattern, entering foo<CR> results in a seg
>>>>> fault.
>>>>>
>>>>> This is on amd64.
>>>>
>>>> Thanks for the report. Of course you want 'export LESS="-g"' here,
>>>> otherwise less(1) won't use the -g flag which is crucial for this crash.
>>>>
>>>> I don't have a fix, but maybe this helps a bit:
>>>>
>>>> From the command line, without environment variable magic and no
>>>> interactive component you can reproduce as follows:
>>>>
>>>> $ echo 'foo\nbar\nfoo\n' > crash
>>>> $ less -g -p '!foo' crash
>>>>
>>>> It's apparently a use-after-free that happens in search_range():
>>>>
>>>> Program terminated with signal SIGSEGV, Segmentation fault.
>>>> #0 0x000009d426e1b35b in create_hilites (linepos=4,
>>>> start_index=-370944992, end_index=-370944989, chpos=0x9d6c5994c80)
>>>> at /usr/src/usr.bin/less/less/../search.c:445
>>>> 445 hl->hl_startpos = linepos + chpos[start_index];
>>>> (gdb) bt
>>>> #0 0x000009d426e1b35b in create_hilites (linepos=4,
>>>> start_index=-370944992, end_index=-370944989, chpos=0x9d6c5994c80)
>>>> at /usr/src/usr.bin/less/less/../search.c:445
>>>> #1 0x000009d426e1b24c in hilite_line (linepos=4, line=0x9d65872bf70
>>>> "bar", line_len=3, chpos=0x9d6c5994c80,
>>>> sp=0x9d642569390 '\337' <repeats 15 times>, <incomplete sequence \337>,
>>>> ep=0x9d642569393 '\337' <repeats 12 times>, <incomplete sequence
>>>> \337>) at /usr/src/usr.bin/less/less/../search.c:494
>>>> #2 0x000009d426e1aa99 in search_range (pos=8, endpos=-1, search_type=257,
>>>> matches=0, maxlines=-1, plinepos=0x7f7ffffe9ff0,
>>>> pendpos=0x0) at /usr/src/usr.bin/less/less/../search.c:804
>>>> #3 0x000009d426e1a258 in search (search_type=257, pattern=0x9d42702ca40
>>>> <cmdbuf> "foo", n=1)
>>>> at /usr/src/usr.bin/less/less/../search.c:925
>>>> #4 0x000009d426e0a182 in multi_search (pattern=0x9d42702ca40 <cmdbuf>
>>>> "foo", n=1) at /usr/src/usr.bin/less/less/../command.c:815
>>>> #5 0x000009d426e0a779 in exec_mca () at
>>>> /usr/src/usr.bin/less/less/../command.c:189
>>>> #6 0x000009d426e09d03 in mca_char (c=10) at
>>>> /usr/src/usr.bin/less/less/../command.c:532
>>>> #7 0x000009d426e08865 in commands () at
>>>> /usr/src/usr.bin/less/less/../command.c:971
>>>> #8 0x000009d426e010f2 in main (argc=-1, argv=0x7f7ffffea200) at
>>>> /usr/src/usr.bin/less/less/../main.c:274
>>>>
>>>
>>> I took a closer look earlier today. As I see it, {start,end}_index does
>>> not get updated inside match_pattern() since we're looking for inverted
>>> matches, i.e. when regexec() indicates no match we actually got a match.
>>> Instead, the indices could be set to NULL up front and the corresponding
>>> NULL-check moved into the loop since match_pattern() is called
>>> repeatedly. Tested with and without `-g` for both normal and inverted
>>> search.
>>>
>>> Index: pattern.c
>>> ===================================================================
>>> RCS file: /cvs/src/usr.bin/less/pattern.c,v
>>> retrieving revision 1.9
>>> diff -u -p -r1.9 pattern.c
>>> --- pattern.c 21 Nov 2015 13:29:12 -0000 1.9
>>> +++ pattern.c 28 Jul 2017 11:31:34 -0000
>>> @@ -122,6 +122,8 @@ match_pattern(void *pattern, char *tpatt
>>> rm.rm_so = 0;
>>> rm.rm_eo = line_len;
>>> #endif
>>> + *sp = NULL;
>>> + *ep = NULL;
>>> matched = !regexec(spattern, line, 1, &rm, flags);
>>> if (matched) {
>>> *sp = line + rm.rm_so;
>>> Index: search.c
>>> ===================================================================
>>> RCS file: /cvs/src/usr.bin/less/search.c,v
>>> retrieving revision 1.18
>>> diff -u -p -r1.18 search.c
>>> --- search.c 17 Sep 2016 15:06:41 -0000 1.18
>>> +++ search.c 28 Jul 2017 11:31:34 -0000
>>> @@ -477,8 +477,6 @@ hilite_line(off_t linepos, char *line, i
>>> char *searchp;
>>> char *line_end = line + line_len;
>>>
>>> - if (sp == NULL || ep == NULL)
>>> - return;
>>> /*
>>> * sp and ep delimit the first match in the line.
>>> * Mark the corresponding file positions, then
>>> @@ -491,6 +489,9 @@ hilite_line(off_t linepos, char *line, i
>>> */
>>> searchp = line;
>>> do {
>>> + if (sp == NULL || ep == NULL)
>>> + return;
>>> +
>>> create_hilites(linepos, (intptr_t)sp - (intptr_t)line,
>>> (intptr_t)ep - (intptr_t)line, chpos);
>>> /*
>>>
