[Libguestfs] [PATCH v1] ldmtool: fix NULL pointer dereference

Vincent Mailhol
Mon, 19 Jun 2023 14:36:05 -0000

If /sys/block can not be opened, get_devices() returns NULL.

cmdline() does not check this result and below code snippet:

          scanned = get_devices();
          devices = (gchar **) scanned->data;

results in a segmentation fault.

Add a check on scanned.

Relevant logs:

  Unable to open /sys/block: No such file or directory
  [    0.777352] ldmtool[164]: segfault at 0 ip 0000563a225cd6a5 sp
00007ffe54965a60 error 4 in ldmtool[563a225cb000+3000]
  [    0.778278] Code: 18 64 48 33 1c 25 28 00 00 00 75 5e 48 83 c4 28 5b 5d 41
5c 41 5d 41 5e 41 5f c3 66 2e 0f 1f 84 00 00 00 00 00 e8 db fd ff ff <4c>
8b 20 48 89 44 24 08 4c 89 e7 e8 0b e1 ff ff 45 31 c0 4c 89 e1

Fixes: 25d9635e4ee5 ("Add ldmtool")
Signed-off-by: Vincent Mailhol <mailhol.vincent at wanadoo.fr>
---
This thread did not yet show-up in
  https://listman.redhat.com/archives/libguestfs/2023-June/subject.html
not sure why.

For this reason, I couln't add a link reference.
---
 src/ldmtool.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/ldmtool.c b/src/ldmtool.c
index 6957c1a..87aaccc 100644
--- a/src/ldmtool.c
+++ b/src/ldmtool.c
@@ -746,6 +746,8 @@ cmdline(LDM * const ldm, gchar **devices,
     GArray * scanned = NULL;
     if (!devices) {
         scanned = get_devices();
+        if (!scanned)
+            goto error;
         devices = (gchar **) scanned->data;
     }

--
2.25.1