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Subject[PATCH v2] FS-Cache: fix buffer size for decimal value of special cookie type
Date
When building object-list.o, gcc (version 7) raises a warning on the
sprintf call in fscache_objlist_show:

CC fs/fscache/object-list.o
fs/fscache/object-list.c: In function ‘fscache_objlist_show’:
fs/fscache/object-list.c:265:19: warning: ‘sprintf’ may write a
terminating nul past the end of the destination [-Wformat-overflow=]
sprintf(_type, "%02u", cookie->def->type);
^~~~~~
fs/fscache/object-list.c:265:4: note: ‘sprintf’ output between 3 and 4
bytes into a destination of size 3
sprintf(_type, "%02u", cookie->def->type);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Moreover, the documentation says that value for special cookies is a
hexadecimal value (see Documentation/filesystems/caching/fscache.txt).

Increasing the buffer size to use a decimal value fixes the problem
without any effect on userland tools. Also, this patch updates the
documentation.

Signed-off-by: Jérémy Lefaure <jeremy.lefaure@lse.epita.fr>
---
v2:
_ keep decimal value
_ fix _type buffer size
_ fix documentation

I didn't have the time to test this patch yet but everything should be fine.


Documentation/filesystems/caching/fscache.txt | 2 +-
fs/fscache/object-list.c | 10 +++++-----
2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/Documentation/filesystems/caching/fscache.txt b/Documentation/filesystems/caching/fscache.txt
index 50f0a5757f48..9c3df61b3c16 100644
--- a/Documentation/filesystems/caching/fscache.txt
+++ b/Documentation/filesystems/caching/fscache.txt
@@ -374,7 +374,7 @@ and the second set of columns describe the object's cookie, if present:
COLUMN DESCRIPTION
=============== =======================================================
NETFS_COOKIE_DEF Name of netfs cookie definition
- TY Cookie type (IX - index, DT - data, hex - special)
+ TY Cookie type (IX - index, DT - data, decimal - special)
FL Cookie flags
NETFS_DATA Netfs private data stored in the cookie
OBJECT_KEY Object key } 1 column, with separating comma
diff --git a/fs/fscache/object-list.c b/fs/fscache/object-list.c
index 67f940892ef8..3452d7dbf1e1 100644
--- a/fs/fscache/object-list.c
+++ b/fs/fscache/object-list.c
@@ -169,7 +169,7 @@ static int fscache_objlist_show(struct seq_file *m, void *v)
struct fscache_object *obj = v;
struct fscache_cookie *cookie;
unsigned long config = data->config;
- char _type[3], *type;
+ char _type[4], *type;
u8 *buf = data->buf, *p;

if ((unsigned long) v == 1) {
@@ -194,7 +194,7 @@ static int fscache_objlist_show(struct seq_file *m, void *v)
if ((unsigned long) v == 2) {
seq_puts(m, "======== ======== ==== ===== === === === == ====="
" == == == ="
- " | ================ == == ================");
+ " | ================ === == ================");
if (config & (FSCACHE_OBJLIST_CONFIG_KEY |
FSCACHE_OBJLIST_CONFIG_AUX))
seq_puts(m, " ================");
@@ -256,13 +256,13 @@ static int fscache_objlist_show(struct seq_file *m, void *v)

switch (cookie->def->type) {
case 0:
- type = "IX";
+ type = " IX";
break;
case 1:
- type = "DT";
+ type = " DT";
break;
default:
- sprintf(_type, "%02u", cookie->def->type);
+ sprintf(_type, "%03u", cookie->def->type);
type = _type;
break;
}
--
2.12.2
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