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* [PATCH] read-cache.c: do not die if mmap fails
@ 2019-07-14  3:01 Varun Naik
  2019-07-14 18:59 ` Junio C Hamano
  0 siblings, 1 reply; 2+ messages in thread
From: Varun Naik @ 2019-07-14  3:01 UTC (permalink / raw)
  To: git; +Cc: Varun Naik

do_read_index() mmaps the index, or tries to die with an error message
on failure. It should call xmmap_gently(), which returns MAP_FAILED,
rather than xmmap(), which dies with its own error message.

An easy way to cause this mmap to fail is by setting $GIT_INDEX_FILE to
a path to a directory and then invoking any command that reads from the
index.

Signed-off-by: Varun Naik <vcnaik94@gmail.com>
---
I believe this is the only place that calls xmmap() when it should be
calling xmmap_gently(). There is a related recent commit 3203566a71
("Use xmmap_gently instead of xmmap in use_pack", 2019-05-16).

 read-cache.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/read-cache.c b/read-cache.c
index 22e7b9944e..4e30dafa9d 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -2140,7 +2140,7 @@ int do_read_index(struct index_state *istate, const char *path, int must_exist)
 	if (mmap_size < sizeof(struct cache_header) + the_hash_algo->rawsz)
 		die(_("%s: index file smaller than expected"), path);
 
-	mmap = xmmap(NULL, mmap_size, PROT_READ, MAP_PRIVATE, fd, 0);
+	mmap = xmmap_gently(NULL, mmap_size, PROT_READ, MAP_PRIVATE, fd, 0);
 	if (mmap == MAP_FAILED)
 		die_errno(_("%s: unable to map index file"), path);
 	close(fd);
-- 
2.22.0


^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: [PATCH] read-cache.c: do not die if mmap fails
  2019-07-14  3:01 [PATCH] read-cache.c: do not die if mmap fails Varun Naik
@ 2019-07-14 18:59 ` Junio C Hamano
  0 siblings, 0 replies; 2+ messages in thread
From: Junio C Hamano @ 2019-07-14 18:59 UTC (permalink / raw)
  To: Varun Naik; +Cc: git

Varun Naik <vcnaik94@gmail.com> writes:

> do_read_index() mmaps the index, or tries to die with an error message
> on failure. It should call xmmap_gently(), which returns MAP_FAILED,
> rather than xmmap(), which dies with its own error message.
>
> An easy way to cause this mmap to fail is by setting $GIT_INDEX_FILE to
> a path to a directory and then invoking any command that reads from the
> index.
>
> Signed-off-by: Varun Naik <vcnaik94@gmail.com>
> ---
> I believe this is the only place that calls xmmap() when it should be
> calling xmmap_gently(). There is a related recent commit 3203566a71
> ("Use xmmap_gently instead of xmmap in use_pack", 2019-05-16).

Nice find and thanks for checking other callsites of xmmap().

>
>  read-cache.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/read-cache.c b/read-cache.c
> index 22e7b9944e..4e30dafa9d 100644
> --- a/read-cache.c
> +++ b/read-cache.c
> @@ -2140,7 +2140,7 @@ int do_read_index(struct index_state *istate, const char *path, int must_exist)
>  	if (mmap_size < sizeof(struct cache_header) + the_hash_algo->rawsz)
>  		die(_("%s: index file smaller than expected"), path);
>  
> -	mmap = xmmap(NULL, mmap_size, PROT_READ, MAP_PRIVATE, fd, 0);
> +	mmap = xmmap_gently(NULL, mmap_size, PROT_READ, MAP_PRIVATE, fd, 0);
>  	if (mmap == MAP_FAILED)
>  		die_errno(_("%s: unable to map index file"), path);
>  	close(fd);

^ permalink raw reply	[flat|nested] 2+ messages in thread

end of thread, other threads:[~2019-07-14 18:59 UTC | newest]

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2019-07-14  3:01 [PATCH] read-cache.c: do not die if mmap fails Varun Naik
2019-07-14 18:59 ` Junio C Hamano

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