[PATCH net 4/9] net/mlx5: fw_tracer, Handle escaped percent properly

[Tariq Toukan <tariqt@nvidia.com>]

From: Shay Drory <shayd@nvidia.com>

The firmware tracer's format string validation and parameter counting
did not properly handle escaped percent signs (%%). This caused
fw_tracer to count more parameters when trace format strings contained
literal percent characters.

To fix it, allow %% to pass string validation and skip %% sequences when
counting parameters since they represent literal percent signs rather
than format specifiers.

Fixes: 70dd6fdb8987 ("net/mlx5: FW tracer, parse traces and kernel tracing support")
Signed-off-by: Shay Drory <shayd@nvidia.com>
Reported-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Moshe Shemesh <moshe@nvidia.com>
Closes: https://lore.kernel.org/netdev/hanz6rzrb2bqbplryjrakvkbmv4y5jlmtthnvi3thg5slqvelp@t3s3erottr6s/
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
---
 .../mellanox/mlx5/core/diag/fw_tracer.c       | 20 +++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/diag/fw_tracer.c b/drivers/net/ethernet/mellanox/mlx5/core/diag/fw_tracer.c
index b415dfe5de45..6b4ec457ce22 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/diag/fw_tracer.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/diag/fw_tracer.c
@@ -368,11 +368,11 @@ static bool mlx5_is_valid_spec(const char *str)
 	while (isdigit(*str) || *str == '#' || *str == '.' || *str == 'l')
 		str++;
 
-	/* Check if it's a valid integer/hex specifier:
+	/* Check if it's a valid integer/hex specifier or %%:
 	 * Valid formats: %x, %d, %i, %u, etc.
 	 */
 	if (*str != 'x' && *str != 'X' && *str != 'd' && *str != 'i' &&
-	    *str != 'u' && *str != 'c')
+	    *str != 'u' && *str != 'c' && *str != '%')
 		return false;
 
 	return true;
@@ -390,7 +390,11 @@ static bool mlx5_tracer_validate_params(const char *str)
 		if (!mlx5_is_valid_spec(substr + 1))
 			return false;
 
-		substr = strstr(substr + 1, PARAM_CHAR);
+		if (*(substr + 1) == '%')
+			substr = strstr(substr + 2, PARAM_CHAR);
+		else
+			substr = strstr(substr + 1, PARAM_CHAR);
+
 	}
 
 	return true;
@@ -469,11 +473,15 @@ static int mlx5_tracer_get_num_of_params(char *str)
 		substr = strstr(pstr, VAL_PARM);
 	}
 
-	/* count all the % characters */
+	/* count all the % characters, but skip %% (escaped percent) */
 	substr = strstr(str, PARAM_CHAR);
 	while (substr) {
-		num_of_params += 1;
-		str = substr + 1;
+		if (*(substr + 1) != '%') {
+			num_of_params += 1;
+			str = substr + 1;
+		} else {
+			str = substr + 2;
+		}
 		substr = strstr(str, PARAM_CHAR);
 	}
 
-- 
2.31.1