Patchwork PowerPC: kernel: memory access violation when rtas_data_buf contents are more than 1026

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Submitter Chen Gang
Date April 23, 2013, 3:12 a.m.
Message ID <5175FC36.4060308@asianux.com>
Download mbox | patch
Permalink /patch/238746/
State Superseded
Delegated to: Benjamin Herrenschmidt
Headers show

Comments

Chen Gang - April 23, 2013, 3:12 a.m.
need set '\0' for 'local_buffer'.

SPLPAR_MAXLENGTH is 1026, RTAS_DATA_BUF_SIZE is 4096. so the contents of
rtas_data_buf may truncated in memcpy.

if contents are really truncated.
  the splpar_strlen is more than 1026. the next while loop checking will
  not find the end of buffer. that will cause memory access violation.


Signed-off-by: Chen Gang <gang.chen@asianux.com>
---
 arch/powerpc/kernel/lparcfg.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
Vasant Hegde - April 24, 2013, 6:28 a.m.
On 04/23/2013 08:42 AM, Chen Gang wrote:
>
> need set '\0' for 'local_buffer'.
>
> SPLPAR_MAXLENGTH is 1026, RTAS_DATA_BUF_SIZE is 4096. so the contents of
> rtas_data_buf may truncated in memcpy.
>
> if contents are really truncated.
>    the splpar_strlen is more than 1026. the next while loop checking will
>    not find the end of buffer. that will cause memory access violation.
>

Per parameter length in ibm,get-system-parameter RTAS call is limited to 1026 
bytes (1024 bytes of data + 2 bytes  length). And 'rtas_data_buf' was set to 0 
(first 1026 bytes) before call RTAS call. At the worst if we get junk in RTAS 
output length field helps to exit from the while loop. So I don't think we need 
this patch.

-Vasant

>
> Signed-off-by: Chen Gang<gang.chen@asianux.com>
> ---
>   arch/powerpc/kernel/lparcfg.c |    1 +
>   1 files changed, 1 insertions(+), 0 deletions(-)
>
> diff --git a/arch/powerpc/kernel/lparcfg.c b/arch/powerpc/kernel/lparcfg.c
> index 801a757..d92f387 100644
> --- a/arch/powerpc/kernel/lparcfg.c
> +++ b/arch/powerpc/kernel/lparcfg.c
> @@ -299,6 +299,7 @@ static void parse_system_parameter_string(struct seq_file *m)
>   				__pa(rtas_data_buf),
>   				RTAS_DATA_BUF_SIZE);
>   	memcpy(local_buffer, rtas_data_buf, SPLPAR_MAXLENGTH);
> +	local_buffer[SPLPAR_MAXLENGTH - 1] = '\0';
>   	spin_unlock(&rtas_data_buf_lock);
>
>   	if (call_status != 0) {

Patch

diff --git a/arch/powerpc/kernel/lparcfg.c b/arch/powerpc/kernel/lparcfg.c
index 801a757..d92f387 100644
--- a/arch/powerpc/kernel/lparcfg.c
+++ b/arch/powerpc/kernel/lparcfg.c
@@ -299,6 +299,7 @@  static void parse_system_parameter_string(struct seq_file *m)
 				__pa(rtas_data_buf),
 				RTAS_DATA_BUF_SIZE);
 	memcpy(local_buffer, rtas_data_buf, SPLPAR_MAXLENGTH);
+	local_buffer[SPLPAR_MAXLENGTH - 1] = '\0';
 	spin_unlock(&rtas_data_buf_lock);
 
 	if (call_status != 0) {