Re: [PATCH] Memory leak in tpm_ascii_bios_measurements_open() fix.

[Reiner Sailer]

Jesper,

thank you very much for finding this error and for posting a patch 
proposal. Since Kylene is not online, I am responding. Please see my 
inlines and an alternative patch proposal below.

Jesper Juhl <jesper.juhl@xxxxxxxxx> wrote on 07/18/2007 07:11:54 PM:

> Ehlo,
>
> Coverity found a memory leak in tpm_ascii_bios_measurements_open().
>
> If "read_log(log)" fails, then we may leak 'log' and
> 'log->bios_event_log'.
>
> This patch should fix it, but please double check it. I don't know
> this code very well and the patch has only been compile tested.
>
>
> Signed-off-by: Jesper Juhl <jesper.juhl@xxxxxxxxx>
> ---
>
>  drivers/char/tpm/tpm_bios.c |   11 ++++++++---
>  1 files changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm_bios.c b/drivers/char/tpm/tpm_bios.c
> index 4eba32b..4b26ce4 100644
> --- a/drivers/char/tpm/tpm_bios.c
> +++ b/drivers/char/tpm/tpm_bios.c
> @@ -427,7 +427,7 @@ static int
> tpm_ascii_bios_measurements_open(struct inode *inode,
>        return -ENOMEM;
>  
>     if ((err = read_log(log)))
> -      return err;
> +      goto out_free;


log->bios_event_log should not be pointing to allocated memory here
(seems cleaner if read_log cleans its allocated memory in the error case)
---> just free log


>
>     /* now register seq file */
>     err = seq_open(file, &tpm_ascii_b_measurments_seqops);
> @@ -435,10 +435,15 @@ static int
> tpm_ascii_bios_measurements_open(struct inode *inode,
>        seq = file->private_data;
>        seq->private = log;
>     } else {
> -      kfree(log->bios_event_log);
> -      kfree(log);
> +      goto out_free;
>     }
> +
> +out:
>     return err;
> +out_free:
> +   kfree(log->bios_event_log);
> +   kfree(log);
> +   goto out;
>  }
>  
>  const struct file_operations tpm_ascii_bios_measurements_ops = {
>
>

The following patch should be sufficient to fix the problem you discovered:
---
drivers/char/tpm/tpm_bios.c |    5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

Index: linux-2.6.22-rc7/drivers/char/tpm/tpm_bios.c
===================================================================
--- linux-2.6.22-rc7.orig/drivers/char/tpm/tpm_bios.c
+++ linux-2.6.22-rc7/drivers/char/tpm/tpm_bios.c
@@ -426,9 +426,10 @@ static int tpm_ascii_bios_measurements_o
    if (!log)
        return -ENOMEM;

-    if ((err = read_log(log)))
+    if ((err = read_log(log))) {
+        kfree(log);
        return err;
-
+    }
    /* now register seq file */
    err = seq_open(file, &tpm_ascii_b_measurments_seqops);
    if (!err) {

Do you agree?

Greetings
Reiner

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