The current implementation will leak a byte to the log via memmove. The
specified 27 bytes are off-by-one, as the payload is 25 bytes, and the
termination character is only one byte large. To avoid this, factor out
the error message, and furthermore make the second parameter of the
append_entry function const.
Fixes: 4562236b3bc0 ("drm/amd/dc: Add dc display driver (v2)")
The full trace is as follows:
In function ‘memmove’,
from ‘append_entry’ at
drivers/gpu/drm/amd/display/dc/basics/logger.c:257:2,
from ‘dm_logger_append_va’ at
drivers/gpu/drm/amd/display/dc/basics/logger.c:348:4
detected read beyond size of object passed as 2nd parameter
Signed-off-by: Norbert Manthey <[email protected]>
Cc: Alex Deucher <[email protected]>
Cc: "Christian König" <[email protected]>
Cc: "David (ChunMing) Zhou" <[email protected]>
Cc: David Airlie <[email protected]>
Cc: Harry Wentland <[email protected]>
Cc: Tony Cheng <[email protected]>
Cc: Yongqiang Sun <[email protected]>
Cc: Aric Cyr <[email protected]>
Cc: Colin Ian King <[email protected]>
Cc: Corbin McElhanney <[email protected]>
Cc: Jordan Lazare <[email protected]>
Cc: Dmytro Laktyushkin <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
---
drivers/gpu/drm/amd/display/dc/basics/logger.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/amd/display/dc/basics/logger.c b/drivers/gpu/drm/amd/display/dc/basics/logger.c
index 180a9d6..958070c 100644
--- a/drivers/gpu/drm/amd/display/dc/basics/logger.c
+++ b/drivers/gpu/drm/amd/display/dc/basics/logger.c
@@ -243,7 +243,7 @@ static void log_heading(struct log_entry *entry)
static void append_entry(
struct log_entry *entry,
- char *buffer,
+ const char *buffer,
uint32_t buf_size)
{
if (!entry->buf ||
@@ -345,7 +345,9 @@ void dm_logger_append_va(
if (size < LOG_MAX_LINE_SIZE - 1) {
append_entry(entry, buffer, size);
} else {
- append_entry(entry, "LOG_ERROR, line too long\n", 27);
+ static const char msg[] = "LOG_ERROR, line too long\n";
+
+ append_entry(entry, msg, sizeof(msg));
}
}
}
--
2.7.4
Amazon Development Center Germany GmbH
Berlin - Dresden - Aachen
main office: Krausenstr. 38, 10117 Berlin
Geschaeftsfuehrer: Dr. Ralf Herbrich, Christian Schlaeger
Ust-ID: DE289237879
Eingetragen am Amtsgericht Charlottenburg HRB 149173 B
On Fri, 2018-02-16 at 10:43 +0100, Norbert Manthey wrote:
> The current implementation will leak a byte to the log via memmove. The
> specified 27 bytes are off-by-one, as the payload is 25 bytes, and the
> termination character is only one byte large. To avoid this, factor out
> the error message, and furthermore make the second parameter of the
> append_entry function const.
>
> Fixes: 4562236b3bc0 ("drm/amd/dc: Add dc display driver (v2)")
>
> The full trace is as follows:
>
> In function ‘memmove’,
> from ‘append_entry’ at
> drivers/gpu/drm/amd/display/dc/basics/logger.c:257:2,
> from ‘dm_logger_append_va’ at
> drivers/gpu/drm/amd/display/dc/basics/logger.c:348:4
> detected read beyond size of object passed as 2nd parameter
>
> Signed-off-by: Norbert Manthey <[email protected]>
That same code exists in a different form in at least 4.15 so
Cc: [email protected]
> Cc: Alex Deucher <[email protected]>
> Cc: "Christian König" <[email protected]>
> Cc: "David (ChunMing) Zhou" <[email protected]>
> Cc: David Airlie <[email protected]>
> Cc: Harry Wentland <[email protected]>
> Cc: Tony Cheng <[email protected]>
> Cc: Yongqiang Sun <[email protected]>
> Cc: Aric Cyr <[email protected]>
> Cc: Colin Ian King <[email protected]>
> Cc: Corbin McElhanney <[email protected]>
> Cc: Jordan Lazare <[email protected]>
> Cc: Dmytro Laktyushkin <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
>
> ---
> drivers/gpu/drm/amd/display/dc/basics/logger.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/display/dc/basics/logger.c b/drivers/gpu/drm/amd/display/dc/basics/logger.c
> index 180a9d6..958070c 100644
> --- a/drivers/gpu/drm/amd/display/dc/basics/logger.c
> +++ b/drivers/gpu/drm/amd/display/dc/basics/logger.c
> @@ -243,7 +243,7 @@ static void log_heading(struct log_entry *entry)
>
> static void append_entry(
> struct log_entry *entry,
> - char *buffer,
> + const char *buffer,
> uint32_t buf_size)
> {
> if (!entry->buf ||
> @@ -345,7 +345,9 @@ void dm_logger_append_va(
> if (size < LOG_MAX_LINE_SIZE - 1) {
> append_entry(entry, buffer, size);
> } else {
> - append_entry(entry, "LOG_ERROR, line too long\n", 27);
> + static const char msg[] = "LOG_ERROR, line too long\n";
> +
> + append_entry(entry, msg, sizeof(msg));
> }
> }
> }