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Subject[099/107] scm: lower SCM_MAX_FD
2.6.32-longterm review patch.  If anyone has any objections, please let us know.

------------------

From: Eric Dumazet <eric.dumazet@gmail.com>

commit bba14de98753cb6599a2dae0e520714b2153522d upstream.

Lower SCM_MAX_FD from 255 to 253 so that allocations for scm_fp_list are
halved. (commit f8d570a4 added two pointers in this structure)

scm_fp_dup() should not copy whole structure (and trigger kmemcheck
warnings), but only the used part. While we are at it, only allocate
needed size.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
include/net/scm.h | 5 +++--
net/core/scm.c | 10 ++++++----
2 files changed, 9 insertions(+), 6 deletions(-)

--- a/include/net/scm.h
+++ b/include/net/scm.h
@@ -10,12 +10,13 @@
/* Well, we should have at least one descriptor open
* to accept passed FDs 8)
*/
-#define SCM_MAX_FD 255
+#define SCM_MAX_FD 253

struct scm_fp_list
{
struct list_head list;
- int count;
+ short count;
+ short max;
struct file *fp[SCM_MAX_FD];
};

--- a/net/core/scm.c
+++ b/net/core/scm.c
@@ -78,10 +78,11 @@ static int scm_fp_copy(struct cmsghdr *c
return -ENOMEM;
*fplp = fpl;
fpl->count = 0;
+ fpl->max = SCM_MAX_FD;
}
fpp = &fpl->fp[fpl->count];

- if (fpl->count + num > SCM_MAX_FD)
+ if (fpl->count + num > fpl->max)
return -EINVAL;

/*
@@ -302,11 +303,12 @@ struct scm_fp_list *scm_fp_dup(struct sc
if (!fpl)
return NULL;

- new_fpl = kmalloc(sizeof(*fpl), GFP_KERNEL);
+ new_fpl = kmemdup(fpl, offsetof(struct scm_fp_list, fp[fpl->count]),
+ GFP_KERNEL);
if (new_fpl) {
- for (i=fpl->count-1; i>=0; i--)
+ for (i = 0; i < fpl->count; i++)
get_file(fpl->fp[i]);
- memcpy(new_fpl, fpl, sizeof(*fpl));
+ new_fpl->max = new_fpl->count;
}
return new_fpl;
}



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