Re: [BUG] parse_object() does not behave as documented
Ping?
Samuel Bronson naes...@gmail.com writes:
[Hmm, nobody seems ot have commented on this analysis; maybe reposting
it with a subject containing [BUG] will help?]
Samuel Bronson naes...@gmail.com writes:
The following message is a courtesy copy of an article
that has been posted to gmane.comp.version-control.git as well.
Oh, I forgot to provide any analysis of the problem. Oops.
It may be just as well, though; I was tired enough that I might have
botched it in any case. So, have an analysis:
While inflate errors are obviously NOT GOOD, and should perhaps be
instantly fatal for most commands, git fsck is something of a special
case because it is useful to have *it* report as many corrupt objects as
possible in one run.
Unfortunately, this is not currently the case, as shown by the provided
testcase.
The output for this testcase is:
,
| checking known breakage:
| hash1=
| hash2=fffe
| mkdir -p .git/objects/ff
| echo not-zlib $(sha1_file $hash1)
| test_when_finished remove_object $hash1
| echo not-zlib $(sha1_file $hash2)
| test_when_finished remove_object $hash2
|
| # Return value is not documented
| test_might_fail git fsck 2out
| cat out echo ==
| grep $hash1.*corrupt out
| grep $hash2.*corrupt out
|
| error: inflate: data stream error (incorrect header check)
| error: unable to unpack header
| error: inflate: data stream error (incorrect header check)
| fatal: loose object (stored
| in .git/objects/ff/ff) is
| corrupt
| ==
| fatal: loose object (stored
| in .git/objects/ff/ff) is
| corrupt
| not ok 5 - fsck survives inflate errors # TODO known breakage
`
If I flip it from expect_failure to expect_success and run the test with
-i, then go into the trash directory and run gdb ../../git-fsck, I can
obtain this (thoroughly rehearsed trimmed) gdb transcript:
,
| % gdb ../../git-fsck
| GNU gdb (Debian 7.7.1-3) 7.7.1
...
| Reading symbols from ../../git-fsck...done.
| (gdb) break error
| Breakpoint 1 at 0x813d24c: file usage.c, line 143.
| (gdb) break die
| Breakpoint 2 at 0x813d152: file usage.c, line 94.
| (gdb) run
| Starting program: /home/naesten/hacking/git/git-fsck
| [Thread debugging using libthread_db enabled]
| Using host libthread_db library
| /lib/i386-linux-gnu/i686/cmov/libthread_db.so.1.
| Checking object directories: 100% (256/256), done.
|
| Breakpoint 1, error (err=0x8182f7a inflate: %s (%s)) at usage.c:143
| 143 {
| (gdb) bt
| #0 error (err=0x8182f7a inflate: %s (%s)) at usage.c:143
| #1 0x081452ff in git_inflate (strm=0xbfffe6b8, flush=0)
| at zlib.c:144
| #2 0x08125367 in unpack_sha1_header (stream=optimized out,
| map=optimized out, mapsize=optimized out,
| buffer=optimized out, bufsiz=optimized out)
| at sha1_file.c:1515
| #3 0x08125546 in sha1_loose_object_info (
| sha1=sha1@entry=0x82659d4 '\377' repeats 20 times,
| oi=oi@entry=0xbfffe788) at sha1_file.c:2528
| #4 0x08126b2d in sha1_object_info_extended (
| sha1=0x82659d4 '\377' repeats 20 times, oi=0xbfffe788, flags=1)
| at sha1_file.c:2565
| #5 0x0812666f in sha1_object_info (
| sha1=0x82659d4 '\377' repeats 20 times, sizep=0x0)
| at sha1_file.c:2601
| #6 0x080f6941 in parse_object (
| sha1=0x82659d4 '\377' repeats 20 times) at object.c:247
| #7 0x080758ac in fsck_sha1 (
| sha1=sha1@entry=0x82659d4 '\377' repeats 20 times)
| at builtin/fsck.c:333
...
| (gdb) c
| Continuing.
| error: inflate: data stream error (incorrect header check)
|
| Breakpoint 1, error (err=0x817c525 unable to unpack %s header)
| at usage.c:143
| 143 {
| (gdb) bt
| #0 error (err=0x817c525 unable to unpack %s header) at usage.c:143
| #1 0x08125564 in sha1_loose_object_info (
| sha1=sha1@entry=0x82659d4 '\377' repeats 20 times,
| oi=oi@entry=0xbfffe788) at sha1_file.c:2529
| #2 0x08126b2d in sha1_object_info_extended (
| sha1=0x82659d4 '\377' repeats 20 times, oi=0xbfffe788, flags=1)
| at sha1_file.c:2565
| #3 0x0812666f in sha1_object_info (
| sha1=0x82659d4 '\377' repeats 20 times, sizep=0x0)
| at sha1_file.c:2601
| #4 0x080f6941 in parse_object (
| sha1=0x82659d4 '\377' repeats 20 times) at object.c:247
...
| (gdb) frame 4
| #4 0x080f6941 in parse_object (
| sha1=0x82659d4 '\377' repeats 20 times) at object.c:247
| warning: Source file is more recent than executable.
| 247 sha1_object_info(sha1, NULL) == OBJ_BLOB)) { // -- first error
| (gdb) down
| #3 0x0812666f in sha1_object_info (
| sha1=0x82659d4 '\377' repeats 20
[BUG] parse_object() does not behave as documented
[Hmm, nobody seems ot have commented on this analysis; maybe reposting
it with a subject containing [BUG] will help?]
Samuel Bronson naes...@gmail.com writes:
The following message is a courtesy copy of an article
that has been posted to gmane.comp.version-control.git as well.
Oh, I forgot to provide any analysis of the problem. Oops.
It may be just as well, though; I was tired enough that I might have
botched it in any case. So, have an analysis:
While inflate errors are obviously NOT GOOD, and should perhaps be
instantly fatal for most commands, git fsck is something of a special
case because it is useful to have *it* report as many corrupt objects as
possible in one run.
Unfortunately, this is not currently the case, as shown by the provided
testcase.
The output for this testcase is:
,
| checking known breakage:
| hash1=
| hash2=fffe
| mkdir -p .git/objects/ff
| echo not-zlib $(sha1_file $hash1)
| test_when_finished remove_object $hash1
| echo not-zlib $(sha1_file $hash2)
| test_when_finished remove_object $hash2
|
| # Return value is not documented
| test_might_fail git fsck 2out
| cat out echo ==
| grep $hash1.*corrupt out
| grep $hash2.*corrupt out
|
| error: inflate: data stream error (incorrect header check)
| error: unable to unpack header
| error: inflate: data stream error (incorrect header check)
| fatal: loose object (stored
| in .git/objects/ff/ff) is
| corrupt
| ==
| fatal: loose object (stored
| in .git/objects/ff/ff) is
| corrupt
| not ok 5 - fsck survives inflate errors # TODO known breakage
`
If I flip it from expect_failure to expect_success and run the test with
-i, then go into the trash directory and run gdb ../../git-fsck, I can
obtain this (thoroughly rehearsed trimmed) gdb transcript:
,
| % gdb ../../git-fsck
| GNU gdb (Debian 7.7.1-3) 7.7.1
...
| Reading symbols from ../../git-fsck...done.
| (gdb) break error
| Breakpoint 1 at 0x813d24c: file usage.c, line 143.
| (gdb) break die
| Breakpoint 2 at 0x813d152: file usage.c, line 94.
| (gdb) run
| Starting program: /home/naesten/hacking/git/git-fsck
| [Thread debugging using libthread_db enabled]
| Using host libthread_db library
| /lib/i386-linux-gnu/i686/cmov/libthread_db.so.1.
| Checking object directories: 100% (256/256), done.
|
| Breakpoint 1, error (err=0x8182f7a inflate: %s (%s)) at usage.c:143
| 143 {
| (gdb) bt
| #0 error (err=0x8182f7a inflate: %s (%s)) at usage.c:143
| #1 0x081452ff in git_inflate (strm=0xbfffe6b8, flush=0)
| at zlib.c:144
| #2 0x08125367 in unpack_sha1_header (stream=optimized out,
| map=optimized out, mapsize=optimized out,
| buffer=optimized out, bufsiz=optimized out)
| at sha1_file.c:1515
| #3 0x08125546 in sha1_loose_object_info (
| sha1=sha1@entry=0x82659d4 '\377' repeats 20 times,
| oi=oi@entry=0xbfffe788) at sha1_file.c:2528
| #4 0x08126b2d in sha1_object_info_extended (
| sha1=0x82659d4 '\377' repeats 20 times, oi=0xbfffe788, flags=1)
| at sha1_file.c:2565
| #5 0x0812666f in sha1_object_info (
| sha1=0x82659d4 '\377' repeats 20 times, sizep=0x0)
| at sha1_file.c:2601
| #6 0x080f6941 in parse_object (
| sha1=0x82659d4 '\377' repeats 20 times) at object.c:247
| #7 0x080758ac in fsck_sha1 (
| sha1=sha1@entry=0x82659d4 '\377' repeats 20 times)
| at builtin/fsck.c:333
...
| (gdb) c
| Continuing.
| error: inflate: data stream error (incorrect header check)
|
| Breakpoint 1, error (err=0x817c525 unable to unpack %s header)
| at usage.c:143
| 143 {
| (gdb) bt
| #0 error (err=0x817c525 unable to unpack %s header) at usage.c:143
| #1 0x08125564 in sha1_loose_object_info (
| sha1=sha1@entry=0x82659d4 '\377' repeats 20 times,
| oi=oi@entry=0xbfffe788) at sha1_file.c:2529
| #2 0x08126b2d in sha1_object_info_extended (
| sha1=0x82659d4 '\377' repeats 20 times, oi=0xbfffe788, flags=1)
| at sha1_file.c:2565
| #3 0x0812666f in sha1_object_info (
| sha1=0x82659d4 '\377' repeats 20 times, sizep=0x0)
| at sha1_file.c:2601
| #4 0x080f6941 in parse_object (
| sha1=0x82659d4 '\377' repeats 20 times) at object.c:247
...
| (gdb) frame 4
| #4 0x080f6941 in parse_object (
| sha1=0x82659d4 '\377' repeats 20 times) at object.c:247
| warning: Source file is more recent than executable.
| 247 sha1_object_info(sha1, NULL) == OBJ_BLOB)) { // -- first error
| (gdb) down
| #3 0x0812666f in sha1_object_info (
| sha1=0x82659d4 '\377' repeats 20 times, sizep=0x0)
| at sha1_file.c:2601
| 2601 if
