From df0a0f229f732ec392330c60d5b790bc30ea2a35 Mon Sep 17 00:00:00 2001 From: Seyediman Seyedarab Date: Thu, 18 Sep 2025 13:01:58 +0800 Subject: [PATCH] iommu/vt-d: Replace snprintf with scnprintf in dmar_latency_snapshot() [ Upstream commit 75c02a037609f34db17e91be195cedb33b61bae0 ] snprintf() returns the number of bytes that would have been written, not the number actually written. Using this for offset tracking can cause buffer overruns if truncation occurs. Replace snprintf() with scnprintf() to ensure the offset stays within bounds. Since scnprintf() never returns a negative value, and zero is not possible in this context because 'bytes' starts at 0 and 'size - bytes' is DEBUG_BUFFER_SIZE in the first call, which is large enough to hold the string literals used, the return value is always positive. An integer overflow is also completely out of reach here due to the small and fixed buffer size. The error check in latency_show_one() is therefore unnecessary. Remove it and make dmar_latency_snapshot() return void. Signed-off-by: Seyediman Seyedarab Link: https://lore.kernel.org/r/20250731225048.131364-1-ImanDevel@gmail.com Signed-off-by: Lu Baolu Signed-off-by: Joerg Roedel Signed-off-by: Sasha Levin --- drivers/iommu/intel/debugfs.c | 10 ++-------- drivers/iommu/intel/perf.c | 10 ++++------ drivers/iommu/intel/perf.h | 5 ++--- 3 files changed, 8 insertions(+), 17 deletions(-) diff --git a/drivers/iommu/intel/debugfs.c b/drivers/iommu/intel/debugfs.c index 1f925285104e..aa9cfcb6039e 100644 --- a/drivers/iommu/intel/debugfs.c +++ b/drivers/iommu/intel/debugfs.c @@ -562,17 +562,11 @@ DEFINE_SHOW_ATTRIBUTE(ir_translation_struct); static void latency_show_one(struct seq_file *m, struct intel_iommu *iommu, struct dmar_drhd_unit *drhd) { - int ret; - seq_printf(m, "IOMMU: %s Register Base Address: %llx\n", iommu->name, drhd->reg_base_addr); - ret = dmar_latency_snapshot(iommu, debug_buf, DEBUG_BUFFER_SIZE); - if (ret < 0) - seq_puts(m, "Failed to get latency snapshot"); - else - seq_puts(m, debug_buf); - seq_puts(m, "\n"); + dmar_latency_snapshot(iommu, debug_buf, DEBUG_BUFFER_SIZE); + seq_printf(m, "%s\n", debug_buf); } static int latency_show(struct seq_file *m, void *v) diff --git a/drivers/iommu/intel/perf.c b/drivers/iommu/intel/perf.c index 94ee70ac38e3..ae64e1123f25 100644 --- a/drivers/iommu/intel/perf.c +++ b/drivers/iommu/intel/perf.c @@ -113,7 +113,7 @@ static char *latency_type_names[] = { " svm_prq" }; -int dmar_latency_snapshot(struct intel_iommu *iommu, char *str, size_t size) +void dmar_latency_snapshot(struct intel_iommu *iommu, char *str, size_t size) { struct latency_statistic *lstat = iommu->perf_statistic; unsigned long flags; @@ -122,7 +122,7 @@ int dmar_latency_snapshot(struct intel_iommu *iommu, char *str, size_t size) memset(str, 0, size); for (i = 0; i < COUNTS_NUM; i++) - bytes += snprintf(str + bytes, size - bytes, + bytes += scnprintf(str + bytes, size - bytes, "%s", latency_counter_names[i]); spin_lock_irqsave(&latency_lock, flags); @@ -130,7 +130,7 @@ int dmar_latency_snapshot(struct intel_iommu *iommu, char *str, size_t size) if (!dmar_latency_enabled(iommu, i)) continue; - bytes += snprintf(str + bytes, size - bytes, + bytes += scnprintf(str + bytes, size - bytes, "\n%s", latency_type_names[i]); for (j = 0; j < COUNTS_NUM; j++) { @@ -156,11 +156,9 @@ int dmar_latency_snapshot(struct intel_iommu *iommu, char *str, size_t size) break; } - bytes += snprintf(str + bytes, size - bytes, + bytes += scnprintf(str + bytes, size - bytes, "%12lld", val); } } spin_unlock_irqrestore(&latency_lock, flags); - - return bytes; } diff --git a/drivers/iommu/intel/perf.h b/drivers/iommu/intel/perf.h index fd6db8049d1a..1e481e9e4ad0 100644 --- a/drivers/iommu/intel/perf.h +++ b/drivers/iommu/intel/perf.h @@ -41,7 +41,7 @@ void dmar_latency_disable(struct intel_iommu *iommu, enum latency_type type); bool dmar_latency_enabled(struct intel_iommu *iommu, enum latency_type type); void dmar_latency_update(struct intel_iommu *iommu, enum latency_type type, u64 latency); -int dmar_latency_snapshot(struct intel_iommu *iommu, char *str, size_t size); +void dmar_latency_snapshot(struct intel_iommu *iommu, char *str, size_t size); #else static inline int dmar_latency_enable(struct intel_iommu *iommu, enum latency_type type) @@ -65,9 +65,8 @@ dmar_latency_update(struct intel_iommu *iommu, enum latency_type type, u64 laten { } -static inline int +static inline void dmar_latency_snapshot(struct intel_iommu *iommu, char *str, size_t size) { - return 0; } #endif /* CONFIG_DMAR_PERF */