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[PATCH v2] verifiers: fix double close on pgp's sig file descriptor

From: Michael Chang
Subject: [PATCH v2] verifiers: fix double close on pgp's sig file descriptor
Date: Thu, 15 Nov 2018 18:13:11 +0800
User-agent: Mutt/1.10.1 (2018-07-13)

An error emerged as when I was tesing the verifiers branch, so instead
of putting it in pgp prefix, the verifiers is used to reflect what the
patch is based on.

While running verify_detached, grub aborts with error.

verify_detached /@/.snapshots/1/snapshot/boot/grub/grub.cfg

alloc magic is broken at 0x7beea660: 0
Aborted. Press any key to exit.

The error is caused by sig file desciptor been closed twice, first time
in grub_verify_signature() to which it is passed as parameter. Second in
grub_cmd_verify_signature() or in whichever opens the sig file
decriptor. The second close is not consider as bug to me either, as in
common rule of what opens a file has to close it to avoid file
descriptor leakage.

Afterall the design of grub_verify_signature() makes it diffcult to keep
a good trace on opened file descriptor from it's caller. Let's refine
the application interface to accept file path rather than descriptor, in
this way the caller doesn't have to care about closing the descriptor by
delegating it to grub_verify_signature() with full tracing to opened
file descriptor by itself.

Signed-off-by: Michael Chang <address@hidden>

v1 -> v2:

  - drop change in grub_verify_signature_init()
 grub-core/commands/pgp.c | 30 +++++++++++++++---------------
 include/grub/pubkey.h    |  2 +-
 2 files changed, 16 insertions(+), 16 deletions(-)

diff --git a/grub-core/commands/pgp.c b/grub-core/commands/pgp.c
index d5d7c0f0a..5133b4c59 100644
--- a/grub-core/commands/pgp.c
+++ b/grub-core/commands/pgp.c
@@ -684,15 +684,26 @@ grub_pubkey_close (void *ctxt)
-grub_verify_signature (grub_file_t f, grub_file_t sig,
+grub_verify_signature (grub_file_t f, const char *fsig,
                       struct grub_public_key *pkey)
+  grub_file_t sig;
   grub_err_t err;
   struct grub_pubkey_context ctxt;
   grub_uint8_t *readbuf = NULL;
+  sig = grub_file_open (fsig,
+                       GRUB_FILE_TYPE_SIGNATURE
+                       | GRUB_FILE_TYPE_NO_DECOMPRESS);
+  if (!sig)
+    return grub_errno;
   err = grub_verify_signature_init (&ctxt, sig);
   if (err)
-    return err;
+    {
+      grub_file_close (sig);
+      return err;
+    }
   readbuf = grub_zalloc (READBUF_SIZE);
   if (!readbuf)
@@ -806,7 +817,7 @@ static grub_err_t
 grub_cmd_verify_signature (grub_extcmd_context_t ctxt,
                           int argc, char **args)
-  grub_file_t f = NULL, sig = NULL;
+  grub_file_t f = NULL;
   grub_err_t err = GRUB_ERR_NONE;
   struct grub_public_key *pk = NULL;
@@ -844,19 +855,8 @@ grub_cmd_verify_signature (grub_extcmd_context_t ctxt,
       goto fail;
-  sig = grub_file_open (args[1],
-                       GRUB_FILE_TYPE_SIGNATURE
-                       | GRUB_FILE_TYPE_NO_DECOMPRESS);
-  if (!sig)
-    {
-      err = grub_errno;
-      goto fail;
-    }
-  err = grub_verify_signature (f, sig, pk);
+  err = grub_verify_signature (f, args[1], pk);
-  if (sig)
-    grub_file_close (sig);
   if (f)
     grub_file_close (f);
   if (pk)
diff --git a/include/grub/pubkey.h b/include/grub/pubkey.h
index 4a9d04b43..fb8be9cbb 100644
--- a/include/grub/pubkey.h
+++ b/include/grub/pubkey.h
@@ -25,7 +25,7 @@ struct grub_public_key *
 grub_load_public_key (grub_file_t f);
-grub_verify_signature (grub_file_t f, grub_file_t sig,
+grub_verify_signature (grub_file_t f, const char *fsig,
                       struct grub_public_key *pk);

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