On 08/26/2015 11:42 AM, Eric Sandeen wrote:
On 8/26/15 9:33 AM, rjohnston@xxxxxxx wrote:
The call to memset will segfault because the offset for the first
parameter is done twice. We are using pointer math to do the
calculation.
The first time is when calculating oldsize, the size of i2gseg_t
is accounted for.
oldsize = (numsegs - SEGPERHNK) * sizeof(i2gseg_t);
Then in the call to memset, oldsize is again multiplied by the size
of i2gmap_t.
memset(inomap.i2gmap + oldsize, ...)
i2gmap holds the used inodes in each chunk. When there are 2^31 chunk
entries, it could describe 2^31 (1 inode/chunk)- 2^40 (64 inodes/chunk).
With 100s of millions of inodes there are enough entries to wrap the
32 bit variable oldsize.
Switching to use array index notation instead of calculating the
pointer address twice ;) would resolve this issue. The unneeded
local variable oldsize can be removed as well.
Ok, this doesn't explain the type change for numsegs, does it?
Nope that was a typo, as it is an array index I meant to change it from
a signed int (intgen_t) to an unsigned (uint32_t).
Can you walk me through why that's needed? At what point would
numsegs = inomap.hnkmaplen * SEGPERHNK; overflow?
Thanks,
-Eric
---
dump/inomap.c | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)
Index: b/dump/inomap.c
===================================================================
--- a/dump/inomap.c
+++ b/dump/inomap.c
@@ -1125,8 +1125,7 @@ cb_add_inogrp( void *arg1, intgen_t fsfd
lastsegp->segoff = 0;
if (lastsegp->hnkoff == inomap.hnkmaplen) {
- intgen_t numsegs;
- intgen_t oldsize;
+ int64_t numsegs;
inomap.hnkmaplen++;
inomap.hnkmap = (hnk_t *)
@@ -1140,10 +1139,7 @@ cb_add_inogrp( void *arg1, intgen_t fsfd
return -1;
/* zero the new portion of the i2gmap */
- oldsize = (numsegs - SEGPERHNK) * sizeof(i2gseg_t);
-
- memset(inomap.i2gmap + oldsize,
- 0,
+ memset(&inomap.i2gmap[numsegs - SEGPERHNK], 0,
SEGPERHNK * sizeof(i2gseg_t));
}
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