[PATCH 5.11 524/601] wlcore: fix overlapping snprintf arguments in debugfs

Greg Kroah-Hartman
2021-05-12T17:56:51Z

From: Arnd Bergmann <arnd@arndb.de>

[ Upstream commit 7b0e2c4f6be3ec68bf807c84e985e81c21404cd1 ]

gcc complains about undefined behavior in calling snprintf()
with the same buffer as input and output:

drivers/net/wireless/ti/wl18xx/debugfs.c: In function 'diversity_num_of_packets_per_ant_read':
drivers/net/wireless/ti/wl18xx/../wlcore/debugfs.h:86:3: error: 'snprintf' argument 4 overlaps destination object 'buf' [-Werror=restrict]
86 | snprintf(buf, sizeof(buf), "%s[%d] = %d\n", \
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
87 | buf, i, stats->sub.name[i]); \
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/net/wireless/ti/wl18xx/debugfs.c:24:2: note: in expansion of macro 'DEBUGFS_FWSTATS_FILE_ARRAY'
24 | DEBUGFS_FWSTATS_FILE_ARRAY(a, b, c, wl18xx_acx_statistics)
| ^~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/net/wireless/ti/wl18xx/debugfs.c:159:1: note: in expansion of macro 'WL18XX_DEBUGFS_FWSTATS_FILE_ARRAY'
159 | WL18XX_DEBUGFS_FWSTATS_FILE_ARRAY(diversity, num_of_packets_per_ant,

There are probably other ways of handling the debugfs file, without
using on-stack buffers, but a simple workaround here is to remember the
current position in the buffer and just keep printing in there.

Fixes: bcca1bbdd412 ("wlcore: add debugfs macro to help print fw statistics arrays")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20210323125723.1961432-1-arnd@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/wireless/ti/wlcore/boot.c | 13 ++++++++-----
drivers/net/wireless/ti/wlcore/debugfs.h | 7 ++++---
2 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/drivers/net/wireless/ti/wlcore/boot.c b/drivers/net/wireless/ti/wlcore/boot.c
index e14d88e558f0..85abd0a2d1c9 100644
--- a/drivers/net/wireless/ti/wlcore/boot.c
+++ b/drivers/net/wireless/ti/wlcore/boot.c
@@ -72,6 +72,7 @@ static int wlcore_validate_fw_ver(struct wl1271 *wl)
unsigned int *min_ver = (wl->fw_type == WL12XX_FW_TYPE_MULTI) ?
wl->min_mr_fw_ver : wl->min_sr_fw_ver;
char min_fw_str[32] = "";
+ int off = 0;
int i;

/* the chip must be exactly equal */
@@ -105,13 +106,15 @@ static int wlcore_validate_fw_ver(struct wl1271 *wl)
return 0;

fail:
- for (i = 0; i < NUM_FW_VER; i++)
+ for (i = 0; i < NUM_FW_VER && off < sizeof(min_fw_str); i++)
if (min_ver[i] == WLCORE_FW_VER_IGNORE)
- snprintf(min_fw_str, sizeof(min_fw_str),
- "%s*.", min_fw_str);
+ off += snprintf(min_fw_str + off,
+ sizeof(min_fw_str) - off,
+ "*.");
else
- snprintf(min_fw_str, sizeof(min_fw_str),
- "%s%u.", min_fw_str, min_ver[i]);
+ off += snprintf(min_fw_str + off,
+ sizeof(min_fw_str) - off,
+ "%u.", min_ver[i]);

wl1271_error("Your WiFi FW version (%u.%u.%u.%u.%u) is invalid.\n"
"Please use at least FW %s\n"
diff --git a/drivers/net/wireless/ti/wlcore/debugfs.h b/drivers/net/wireless/ti/wlcore/debugfs.h
index b143293e694f..715edfa5f89f 100644
--- a/drivers/net/wireless/ti/wlcore/debugfs.h
+++ b/drivers/net/wireless/ti/wlcore/debugfs.h
@@ -78,13 +78,14 @@ static ssize_t sub## _ ##name## _read(struct file *file, \
struct wl1271 *wl = file->private_data; \
struct struct_type *stats = wl->stats.fw_stats; \
char buf[DEBUGFS_FORMAT_BUFFER_SIZE] = ""; \
+ int pos = 0; \
int i; \
\
wl1271_debugfs_update_stats(wl); \
\
- for (i = 0; i < len; i++) \
- snprintf(buf, sizeof(buf), "%s[%d] = %d\n", \
- buf, i, stats->sub.name[i]); \
+ for (i = 0; i < len && pos < sizeof(buf); i++) \
+ pos += snprintf(buf + pos, sizeof(buf), \
+ "[%d] = %d\n", i, stats->sub.name[i]); \
\
return wl1271_format_buffer(userbuf, count, ppos, "%s", buf); \
} \
--
2.30.2