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iommu/vt-d: Replace snprintf with scnprintf in dmar_latency_snapshot()

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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 <ImanDevel@gmail.com>
Link: https://lore.kernel.org/r/20250731225048.131364-1-ImanDevel@gmail.com
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
This commit is contained in:
Seyediman Seyedarab
2025-09-18 13:01:58 +08:00
committed by Joerg Roedel
parent 1b237f190e
commit 75c02a0376
3 changed files with 8 additions and 17 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
drivers/iommu/intel/debugfs.c
View File

@@ -648,17 +648,11 @@ 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)

10
drivers/iommu/intel/perf.c
View File

@@ -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;
}

5
drivers/iommu/intel/perf.h
View File

@@ -40,7 +40,7 @@ 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)
@@ -64,9 +64,8 @@ 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 */