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fw_cfg: fix memory corruption when all fw_cfg slots are used 

When all the fw_cfg slots are used, a write is made outside the
bounds of the fw_cfg files array as part of the sort algorithm.

Fix it by avoiding an unnecessary array element move.
Fix also an assert while at it.

Signed-off-by: Marcel Apfelbaum <marcel@redhat.com>
Message-Id: <20180108215007.46471-1-marcel@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
This commit is contained in:
Marcel Apfelbaum 2018-01-08 23:50:07 +02:00 committed by Eduardo Habkost
parent d342eb7662
commit d6b6abc51d
1 changed files with 4 additions and 2 deletions
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6
hw/nvram/fw_cfg.c
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@ -784,7 +784,7 @@ void fw_cfg_add_file_callback(FWCfgState *s, const char *filename,
* index and "i - 1" is the one being copied from, thus the
* unusual start and end in the for statement.
*/
for (i = count + 1; i > index; i--) {
for (i = count; i > index; i--) {
s->files->f[i] = s->files->f[i - 1];
s->files->f[i].select = cpu_to_be16(FW_CFG_FILE_FIRST + i);
s->entries[0][FW_CFG_FILE_FIRST + i] =
@ -833,7 +833,6 @@ void *fw_cfg_modify_file(FWCfgState *s, const char *filename,
assert(s->files);
index = be32_to_cpu(s->files->count);
assert(index < fw_cfg_file_slots(s));
for (i = 0; i < index; i++) {
if (strcmp(filename, s->files->f[i].name) == 0) {
@ -843,6 +842,9 @@ void *fw_cfg_modify_file(FWCfgState *s, const char *filename,
return ptr;
}
}
assert(index < fw_cfg_file_slots(s));
/* add new one */
fw_cfg_add_file_callback(s, filename, NULL, NULL, NULL, data, len, true);
return NULL;