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liveupdate: Use refcount_t for FLB reference counts

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Use refcount_t instead of a raw integer to keep track of references on
incoming and outgoing FLBs. Using refcount_t provides protection from
overflow, underflow, and other issues.

Fixes: cab056f2aa ("liveupdate: luo_flb: introduce File-Lifecycle-Bound global state")
Signed-off-by: David Matlack <dmatlack@google.com>
Reviewed-by: Samiullah Khawaja <skhawaja@google.com>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Link: https://lore.kernel.org/r/20260423174032.3140399-2-dmatlack@google.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
This commit is contained in:
David Matlack
2026-04-23 17:40:28 +00:00
committed by Mike Rapoport (Microsoft)
parent a1f8ed3451
commit d2850ff2f8
2 changed files with 12 additions and 13 deletions
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3
include/linux/liveupdate.h
View File

@@ -12,6 +12,7 @@
#include <linux/kho/abi/luo.h>
#include <linux/list.h>
#include <linux/mutex.h>
#include <linux/refcount.h>
#include <linux/rwsem.h>
#include <linux/types.h>
#include <uapi/linux/liveupdate.h>
@@ -175,7 +176,7 @@ struct liveupdate_flb_ops {
* @retrieved: True once the FLB's retrieve() callback has run.
*/
struct luo_flb_private_state {
long count;
refcount_t count;
u64 data;
void *obj;
struct mutex lock;

22
kernel/liveupdate/luo_flb.c
View File

@@ -111,7 +111,7 @@ static int luo_flb_file_preserve_one(struct liveupdate_flb *flb)
struct luo_flb_private *private = luo_flb_get_private(flb);
scoped_guard(mutex, &private->outgoing.lock) {
if (!private->outgoing.count) {
if (!refcount_read(&private->outgoing.count)) {
struct liveupdate_flb_op_args args = {0};
int err;
@@ -126,8 +126,10 @@ static int luo_flb_file_preserve_one(struct liveupdate_flb *flb)
}
private->outgoing.data = args.data;
private->outgoing.obj = args.obj;
refcount_set(&private->outgoing.count, 1);
} else {
refcount_inc(&private->outgoing.count);
}
private->outgoing.count++;
}
return 0;
@@ -138,8 +140,7 @@ static void luo_flb_file_unpreserve_one(struct liveupdate_flb *flb)
struct luo_flb_private *private = luo_flb_get_private(flb);
scoped_guard(mutex, &private->outgoing.lock) {
private->outgoing.count--;
if (!private->outgoing.count) {
if (refcount_dec_and_test(&private->outgoing.count)) {
struct liveupdate_flb_op_args args = {0};
args.flb = flb;
@@ -178,7 +179,7 @@ static int luo_flb_retrieve_one(struct liveupdate_flb *flb)
for (int i = 0; i < fh->header_ser->count; i++) {
if (!strcmp(fh->ser[i].name, flb->compatible)) {
private->incoming.data = fh->ser[i].data;
private->incoming.count = fh->ser[i].count;
refcount_set(&private->incoming.count, fh->ser[i].count);
found = true;
break;
}
@@ -208,12 +209,8 @@ static int luo_flb_retrieve_one(struct liveupdate_flb *flb)
static void luo_flb_file_finish_one(struct liveupdate_flb *flb)
{
struct luo_flb_private *private = luo_flb_get_private(flb);
u64 count;
scoped_guard(mutex, &private->incoming.lock)
count = --private->incoming.count;
if (!count) {
if (refcount_dec_and_test(&private->incoming.count)) {
struct liveupdate_flb_op_args args = {0};
if (!private->incoming.retrieved) {
@@ -652,12 +649,13 @@ void luo_flb_serialize(void)
guard(rwsem_read)(&luo_register_rwlock);
list_private_for_each_entry(gflb, &luo_flb_global.list, private.list) {
struct luo_flb_private *private = luo_flb_get_private(gflb);
long count = refcount_read(&private->outgoing.count);
if (private->outgoing.count > 0) {
if (count > 0) {
strscpy(fh->ser[i].name, gflb->compatible,
sizeof(fh->ser[i].name));
fh->ser[i].data = private->outgoing.data;
fh->ser[i].count = private->outgoing.count;
fh->ser[i].count = count;
i++;
}
}