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md-cache: avoid checking the xattr value buffer with string functions.

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xattrs may very well contain binary, non-text data with leading 0
values. Using strcmp for checking empty values is not the appropriate
thing to do: In the best case, it might treat a binary xattr value
starting with 0 from being cached (and hence also from being reported
back with xattr). In the worst case, we might read beyond the end
of a data blob that does contain any zero byte.

We fix this by checking the length of the data blob and checking
the first byte against 0 if the length is one.

Signed-off-by: Guenther Deschner <gd@samba.org>
Pair-Programmed-With: Michael Adam <obnox@samba.org>
Change-Id: If723c465a630b8a37b6be58782a2724df7ac6b11
BUG: 1476324
Reviewed-on: https://review.gluster.org/17910
Reviewed-by: Michael Adam <obnox@samba.org>
Smoke: Gluster Build System <jenkins@build.gluster.org>
Reviewed-by: Poornima G <pgurusid@redhat.com>
Tested-by: Poornima G <pgurusid@redhat.com>
CentOS-regression: Gluster Build System <jenkins@build.gluster.org>
This commit is contained in:
Günther Deschner 2017-07-28 13:38:16 +02:00 committed by Jeff Darcy
parent e5db980504
commit ab4ffdac9d
2 changed files with 28 additions and 1 deletions
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27
tests/bugs/md-cache/bug-1476324.t Normal file
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@ -0,0 +1,27 @@
#!/bin/bash
. $(dirname $0)/../../include.rc
. $(dirname $0)/../../volume.rc
cleanup;
TEST glusterd;
TEST $CLI volume create $V0 $H0:$B0/${V0}{1,2,3};
TEST $CLI volume start $V0
TEST $CLI volume set $V0 performance.md-cache-timeout 600
TEST $CLI volume set $V0 performance.cache-samba-metadata on
TEST glusterfs --volfile-id=/$V0 --volfile-server=$H0 $M0
TEST touch $M0/file1
TEST "setfattr -n user.DOSATTRIB -v 0sAAOW $M0/file1"
TEST "getfattr -n user.DOSATTRIB $M0/file1 -e base64 | grep -q 0sAAOW"
TEST "setfattr -n user.DOSATTRIB -v 0x00ff $M0/file1"
TEST "getfattr -n user.DOSATTRIB $M0/file1 -e hex | grep -q 0x00ff"
cleanup;

2
xlators/performance/md-cache/src/md-cache.c
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@ -633,7 +633,7 @@ updatefn(dict_t *dict, char *key, data_t *value, void *data)
* not update their cache if the value of a xattr is a 0 byte
* data (i.e. "").
*/
if (!strcmp (value->data, ""))
if (value->len == 1 && value->data[0] == '\0')
continue;
if (dict_set(u->dict, key, value) < 0) {