git/builtin/worktree.c, branch v2.15.2

worktree: check the result of read_in_full()

2017-09-27T06:46:05Z

We try to read "len" bytes into a buffer and just assume that it happened correctly. In practice this should usually be the case, since we just stat'd the file to get the length. But we could be fooled by transient errors or by other processes racily truncating the file. Let's be more careful. There's a slim chance this could catch a real error, but it also prevents people and tools from getting worried while reading the code. Signed-off-by: Jeff King Signed-off-by: Junio C Hamano

worktree: use xsize_t to access file size

2017-09-27T06:45:57Z

To read the "gitdir" file into memory, we stat the file and allocate a buffer. But we store the size in an "int", which may be truncated. We should use a size_t and xsize_t(), which will detect truncation. An overflow is unlikely for a "gitdir" file, but it's a good practice to model. Signed-off-by: Jeff King Reviewed-by: Jonathan Nieder Signed-off-by: Junio C Hamano

add UNLEAK annotation for reducing leak false positives

2017-09-08T06:43:17Z

It's a common pattern in git commands to allocate some memory that should last for the lifetime of the program and then not bother to free it, relying on the OS to throw it away. This keeps the code simple, and it's fast (we don't waste time traversing structures or calling free at the end of the program). But it also triggers warnings from memory-leak checkers like valgrind or LSAN. They know that the memory was still allocated at program exit, but they don't know _when_ the leaked memory stopped being useful. If it was early in the program, then it's probably a real and important leak. But if it was used right up until program exit, it's not an interesting leak and we'd like to suppress it so that we can see the real leaks. This patch introduces an UNLEAK() macro that lets us do so. To understand its design, let's first look at some of the alternatives. Unfortunately the suppression systems offered by leak-checking tools don't quite do what we want. A leak-checker basically knows two things: 1. Which blocks were allocated via malloc, and the callstack during the allocation. 2. Which blocks were left un-freed at the end of the program (and which are unreachable, but more on that later). Their suppressions work by mentioning the function or callstack of a particular allocation, and marking it as OK to leak. So imagine you have code like this: int cmd_foo(...) { /* this allocates some memory */ char *p = some_function(); printf("%s", p); return 0; } You can say "ignore allocations from some_function(), they're not leaks". But that's not right. That function may be called elsewhere, too, and we would potentially want to know about those leaks. So you can say "ignore the callstack when main calls some_function". That works, but your annotations are brittle. In this case it's only two functions, but you can imagine that the actual allocation is much deeper. If any of the intermediate code changes, you have to update the suppression. What we _really_ want to say is that "the value assigned to p at the end of the function is not a real leak". But leak-checkers can't understand that; they don't know about "p" in the first place. However, we can do something a little bit tricky if we make some assumptions about how leak-checkers work. They generally don't just report all un-freed blocks. That would report even globals which are still accessible when the leak-check is run. Instead they take some set of memory (like BSS) as a root and mark it as "reachable". Then they scan the reachable blocks for anything that looks like a pointer to a malloc'd block, and consider that block reachable. And then they scan those blocks, and so on, transitively marking anything reachable from a global as "not leaked" (or at least leaked in a different category). So we can mark the value of "p" as reachable by putting it into a variable with program lifetime. One way to do that is to just mark "p" as static. But that actually affects the run-time behavior if the function is called twice (you aren't likely to call main() twice, but some of our cmd_*() functions are called from other commands). Instead, we can trick the leak-checker by putting the value into _any_ reachable bytes. This patch keeps a global linked-list of bytes copied from "unleaked" variables. That list is reachable even at program exit, which confers recursive reachability on whatever values we unleak. In other words, you can do: int cmd_foo(...) { char *p = some_function(); printf("%s", p); UNLEAK(p); return 0; } to annotate "p" and suppress the leak report. But wait, couldn't we just say "free(p)"? In this toy example, yes. But UNLEAK()'s byte-copying strategy has several advantages over actually freeing the memory: 1. It's recursive across structures. In many cases our "p" is not just a pointer, but a complex struct whose fields may have been allocated by a sub-function. And in some cases (e.g., dir_struct) we don't even have a function which knows how to free all of the struct members. By marking the struct itself as reachable, that confers reachability on any pointers it contains (including those found in embedded structs, or reachable by walking heap blocks recursively. 2. It works on cases where we're not sure if the value is allocated or not. For example: char *p = argc > 1 ? argv[1] : some_function(); It's safe to use UNLEAK(p) here, because it's not freeing any memory. In the case that we're pointing to argv here, the reachability checker will just ignore our bytes. 3. Likewise, it works even if the variable has _already_ been freed. We're just copying the pointer bytes. If the block has been freed, the leak-checker will skip over those bytes as uninteresting. 4. Because it's not actually freeing memory, you can UNLEAK() before we are finished accessing the variable. This is helpful in cases like this: char *p = some_function(); return another_function(p); Writing this with free() requires: int ret; char *p = some_function(); ret = another_function(p); free(p); return ret; But with unleak we can just write: char *p = some_function(); UNLEAK(p); return another_function(p); This patch adds the UNLEAK() macro and enables it automatically when Git is compiled with SANITIZE=leak. In normal builds it's a noop, so we pay no runtime cost. It also adds some UNLEAK() annotations to show off how the feature works. On top of other recent leak fixes, these are enough to get t0000 and t0001 to pass when compiled with LSAN. Note the case in commit.c which actually converts a strbuf_release() into an UNLEAK. This code was already non-leaky, but the free didn't do anything useful, since we're exiting. Converting it to an annotation means that non-leak-checking builds pay no runtime cost. The cost is minimal enough that it's probably not worth going on a crusade to convert these kinds of frees to UNLEAKS. I did it here for consistency with the "sb" leak (though it would have been equally correct to go the other way, and turn them both into strbuf_release() calls). Signed-off-by: Jeff King Signed-off-by: Junio C Hamano

Merge branch 'ab/free-and-null'

2017-06-24T21:28:41Z

A common pattern to free a piece of memory and assign NULL to the pointer that used to point at it has been replaced with a new FREE_AND_NULL() macro. * ab/free-and-null: *.[ch] refactoring: make use of the FREE_AND_NULL() macro coccinelle: make use of the "expression" FREE_AND_NULL() rule coccinelle: add a rule to make "expression" code use FREE_AND_NULL() coccinelle: make use of the "type" FREE_AND_NULL() rule coccinelle: add a rule to make "type" code use FREE_AND_NULL() git-compat-util: add a FREE_AND_NULL() wrapper around free(ptr); ptr = NULL

Merge branch 'bw/config-h'

2017-06-24T21:28:41Z

Fix configuration codepath to pay proper attention to commondir that is used in multi-worktree situation, and isolate config API into its own header file. * bw/config-h: config: don't implicitly use gitdir or commondir config: respect commondir setup: teach discover_git_directory to respect the commondir config: don't include config.h by default config: remove git_config_iter config: create config.h

*.[ch] refactoring: make use of the FREE_AND_NULL() macro

2017-06-16T19:44:09Z

Replace occurrences of `free(ptr); ptr = NULL` which weren't caught by the coccinelle rule. These fall into two categories: - free/NULL assignments one after the other which coccinelle all put on one line, which is functionally equivalent code, but very ugly. - manually spotted occurrences where the NULL assignment isn't right after the free() call. Signed-off-by: Ævar Arnfjörð Bjarmason Signed-off-by: Junio C Hamano

config: don't include config.h by default

2017-06-15T19:56:22Z

Stop including config.h by default in cache.h. Instead only include config.h in those files which require use of the config system. Signed-off-by: Brandon Williams Signed-off-by: Junio C Hamano

Merge branch 'js/plug-leaks'

2017-05-29T03:34:44Z

Fix memory leaks pointed out by Coverity (and people). * js/plug-leaks: (26 commits) checkout: fix memory leak submodule_uses_worktrees(): plug memory leak show_worktree(): plug memory leak name-rev: avoid leaking memory in the `deref` case remote: plug memory leak in match_explicit() add_reflog_for_walk: avoid memory leak shallow: avoid memory leak line-log: avoid memory leak receive-pack: plug memory leak in update() fast-export: avoid leaking memory in handle_tag() mktree: plug memory leaks reported by Coverity pack-redundant: plug memory leak setup_discovered_git_dir(): plug memory leak setup_bare_git_dir(): help static analysis split_commit_in_progress(): simplify & fix memory leak checkout: fix memory leak cat-file: fix memory leak mailinfo & mailsplit: check for EOF while parsing status: close file descriptor after reading git-rebase-todo difftool: address a couple of resource/memory leaks ...

Merge branch 'js/larger-timestamps'

2017-05-16T02:51:59Z

Some platforms have ulong that is smaller than time_t, and our historical use of ulong for timestamp would mean they cannot represent some timestamp that the platform allows. Invent a separate and dedicated timestamp_t (so that we can distingiuish timestamps and a vanilla ulongs, which along is already a good move), and then declare uintmax_t is the type to be used as the timestamp_t. * js/larger-timestamps: archive-tar: fix a sparse 'constant too large' warning use uintmax_t for timestamps date.c: abort if the system time cannot handle one of our timestamps timestamp_t: a new data type for timestamps PRItime: introduce a new "printf format" for timestamps parse_timestamp(): specify explicitly where we parse timestamps t0006 & t5000: skip "far in the future" test when time_t is too limited t0006 & t5000: prepare for 64-bit timestamps ref-filter: avoid using `unsigned long` for catch-all data type

show_worktree(): plug memory leak

2017-05-08T03:18:20Z

The buffer allocated by shorten_unambiguous_ref() needs to be released. Discovered by Coverity. Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano