[PATCH] ufs: core: tracing: Do not dereference pointers in TP_printk()

[PATCH] ufs: core: tracing: Do not dereference pointers in TP_printk()

[Steven Rostedt]

From: Steven Rostedt <rostedt@goodmis.org>

The trace events in drivers/ufs/core/ufs_trace.h were converted to take a
pointer to the hba structure as an argument for the tracepoint and then in
TP_printk() the printing of the dev_name from the ring buffer was
converted to using the dev dereferenced pointer from the hba saved
pointer.

This is not allowed as the TP_printk() is executed at the time the trace
event is read from /sys/kernel/tracing/trace file. That can happen
literally, seconds, minutes, hours, weeks, days, or even months later!
There is no guarantee that the hba pointer will still exist by the time it
is dereferenced when the "trace" file is read.

Instead, save the device name from the hba pointer at the time the
tracepoint is called and place it into the ring buffer event. Then the
TP_printk() can read the name directly from the ring buffer and remove the
possibility that it will read a freed pointer and crash the kernel.

This was detected when testing the trace event code that looks for
TP_printk() parameters doing illegal derferences[1]

[1] https://lore.kernel.org/all/20260630184836.74d477b6@gandalf.local.home/

Cc: stable@vger.kernel.org
Fixes: 583e518e71003 ("scsi: ufs: core: Add hba parameter to trace events")
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 drivers/ufs/core/ufs_trace.h | 36 +++++++++++++++++++++++++++---------
 1 file changed, 27 insertions(+), 9 deletions(-)

diff --git a/drivers/ufs/core/ufs_trace.h b/drivers/ufs/core/ufs_trace.h
index 309ae51b4906..377a3c54b9f5 100644
--- a/drivers/ufs/core/ufs_trace.h
+++ b/drivers/ufs/core/ufs_trace.h
@@ -89,16 +89,18 @@ TRACE_EVENT(ufshcd_clk_gating,
 
 	TP_STRUCT__entry(
 		__field(struct ufs_hba *, hba)
+		__string(dev_name, dev_name(hba->dev))
 		__field(int, state)
 	),
 
 	TP_fast_assign(
+		__assign_str(dev_name);
 		__entry->hba = hba;
 		__entry->state = state;
 	),
 
 	TP_printk("%s: gating state changed to %s",
-		dev_name(__entry->hba->dev),
+		__get_str(dev_name),
 		__print_symbolic(__entry->state, UFSCHD_CLK_GATING_STATES))
 );
 
@@ -111,6 +113,7 @@ TRACE_EVENT(ufshcd_clk_scaling,
 
 	TP_STRUCT__entry(
 		__field(struct ufs_hba *, hba)
+		__string(dev_name, dev_name(hba->dev))
 		__string(state, state)
 		__string(clk, clk)
 		__field(u32, prev_state)
@@ -119,6 +122,7 @@ TRACE_EVENT(ufshcd_clk_scaling,
 
 	TP_fast_assign(
 		__entry->hba = hba;
+		__assign_str(dev_name);
 		__assign_str(state);
 		__assign_str(clk);
 		__entry->prev_state = prev_state;
@@ -126,7 +130,7 @@ TRACE_EVENT(ufshcd_clk_scaling,
 	),
 
 	TP_printk("%s: %s %s from %u to %u Hz",
-		dev_name(__entry->hba->dev), __get_str(state), __get_str(clk),
+		__get_str(dev_name), __get_str(state), __get_str(clk),
 		__entry->prev_state, __entry->curr_state)
 );
 
@@ -138,16 +142,18 @@ TRACE_EVENT(ufshcd_auto_bkops_state,
 
 	TP_STRUCT__entry(
 		__field(struct ufs_hba *, hba)
+		__string(dev_name, dev_name(hba->dev))
 		__string(state, state)
 	),
 
 	TP_fast_assign(
 		__entry->hba = hba;
+		__assign_str(dev_name);
 		__assign_str(state);
 	),
 
 	TP_printk("%s: auto bkops - %s",
-		dev_name(__entry->hba->dev), __get_str(state))
+		__get_str(dev_name), __get_str(state))
 );
 
 DECLARE_EVENT_CLASS(ufshcd_profiling_template,
@@ -158,6 +164,7 @@ DECLARE_EVENT_CLASS(ufshcd_profiling_template,
 
 	TP_STRUCT__entry(
 		__field(struct ufs_hba *, hba)
+		__string(dev_name, dev_name(hba->dev))
 		__string(profile_info, profile_info)
 		__field(s64, time_us)
 		__field(int, err)
@@ -165,13 +172,14 @@ DECLARE_EVENT_CLASS(ufshcd_profiling_template,
 
 	TP_fast_assign(
 		__entry->hba = hba;
+		__assign_str(dev_name);
 		__assign_str(profile_info);
 		__entry->time_us = time_us;
 		__entry->err = err;
 	),
 
 	TP_printk("%s: %s: took %lld usecs, err %d",
-		dev_name(__entry->hba->dev), __get_str(profile_info),
+		__get_str(dev_name), __get_str(profile_info),
 		__entry->time_us, __entry->err)
 );
 
@@ -200,6 +208,7 @@ DECLARE_EVENT_CLASS(ufshcd_template,
 		__field(s64, usecs)
 		__field(int, err)
 		__field(struct ufs_hba *, hba)
+		__string(dev_name, dev_name(hba->dev))
 		__field(int, dev_state)
 		__field(int, link_state)
 	),
@@ -208,13 +217,14 @@ DECLARE_EVENT_CLASS(ufshcd_template,
 		__entry->usecs = usecs;
 		__entry->err = err;
 		__entry->hba = hba;
+		__assign_str(dev_name);
 		__entry->dev_state = dev_state;
 		__entry->link_state = link_state;
 	),
 
 	TP_printk(
 		"%s: took %lld usecs, dev_state: %s, link_state: %s, err %d",
-		dev_name(__entry->hba->dev),
+		__get_str(dev_name),
 		__entry->usecs,
 		__print_symbolic(__entry->dev_state, UFS_PWR_MODES),
 		__print_symbolic(__entry->link_state, UFS_LINK_STATES),
@@ -279,6 +289,7 @@ TRACE_EVENT(ufshcd_command,
 	TP_STRUCT__entry(
 		__field(struct scsi_device *, sdev)
 		__field(struct ufs_hba *, hba)
+		__string(dev_name, dev_name(&sdev->sdev_dev))
 		__field(enum ufs_trace_str_t, str_t)
 		__field(unsigned int, tag)
 		__field(u32, doorbell)
@@ -291,6 +302,7 @@ TRACE_EVENT(ufshcd_command,
 	),
 
 	TP_fast_assign(
+		__assign_str(dev_name);
 		__entry->sdev = sdev;
 		__entry->hba = hba;
 		__entry->str_t = str_t;
@@ -307,7 +319,7 @@ TRACE_EVENT(ufshcd_command,
 	TP_printk(
 		"%s: %s: tag: %u, DB: 0x%x, size: %d, IS: %u, LBA: %llu, opcode: 0x%x (%s), group_id: 0x%x, hwq_id: %d",
 		show_ufs_cmd_trace_str(__entry->str_t),
-		dev_name(&__entry->sdev->sdev_dev), __entry->tag,
+		__get_str(dev_name), __entry->tag,
 		__entry->doorbell, __entry->transfer_len, __entry->intr,
 		__entry->lba, (u32)__entry->opcode, str_opcode(__entry->opcode),
 		(u32)__entry->group_id, __entry->hwq_id
@@ -322,6 +334,7 @@ TRACE_EVENT(ufshcd_uic_command,
 
 	TP_STRUCT__entry(
 		__field(struct ufs_hba *, hba)
+		__string(dev_name, dev_name(hba->dev))
 		__field(enum ufs_trace_str_t, str_t)
 		__field(u32, cmd)
 		__field(u32, arg1)
@@ -331,6 +344,7 @@ TRACE_EVENT(ufshcd_uic_command,
 
 	TP_fast_assign(
 		__entry->hba = hba;
+		__assign_str(dev_name);
 		__entry->str_t = str_t;
 		__entry->cmd = cmd;
 		__entry->arg1 = arg1;
@@ -340,7 +354,7 @@ TRACE_EVENT(ufshcd_uic_command,
 
 	TP_printk(
 		"%s: %s: cmd: 0x%x, arg1: 0x%x, arg2: 0x%x, arg3: 0x%x",
-		show_ufs_cmd_trace_str(__entry->str_t), dev_name(__entry->hba->dev),
+		show_ufs_cmd_trace_str(__entry->str_t), __get_str(dev_name),
 		__entry->cmd, __entry->arg1, __entry->arg2, __entry->arg3
 	)
 );
@@ -353,6 +367,7 @@ TRACE_EVENT(ufshcd_upiu,
 
 	TP_STRUCT__entry(
 		__field(struct ufs_hba *, hba)
+		__string(dev_name, dev_name(hba->dev))
 		__field(enum ufs_trace_str_t, str_t)
 		__array(unsigned char, hdr, 12)
 		__array(unsigned char, tsf, 16)
@@ -361,6 +376,7 @@ TRACE_EVENT(ufshcd_upiu,
 
 	TP_fast_assign(
 		__entry->hba = hba;
+		__assign_str(dev_name);
 		__entry->str_t = str_t;
 		memcpy(__entry->hdr, hdr, sizeof(__entry->hdr));
 		memcpy(__entry->tsf, tsf, sizeof(__entry->tsf));
@@ -369,7 +385,7 @@ TRACE_EVENT(ufshcd_upiu,
 
 	TP_printk(
 		"%s: %s: HDR:%s, %s:%s",
-		show_ufs_cmd_trace_str(__entry->str_t), dev_name(__entry->hba->dev),
+		show_ufs_cmd_trace_str(__entry->str_t), __get_str(dev_name),
 		__print_hex(__entry->hdr, sizeof(__entry->hdr)),
 		show_ufs_cmd_trace_tsf(__entry->tsf_t),
 		__print_hex(__entry->tsf, sizeof(__entry->tsf))
@@ -384,16 +400,18 @@ TRACE_EVENT(ufshcd_exception_event,
 
 	TP_STRUCT__entry(
 		__field(struct ufs_hba *, hba)
+		__string(dev_name, dev_name(hba->dev))
 		__field(u16, status)
 	),
 
 	TP_fast_assign(
 		__entry->hba = hba;
+		__assign_str(dev_name);
 		__entry->status = status;
 	),
 
 	TP_printk("%s: status 0x%x",
-		dev_name(__entry->hba->dev), __entry->status
+		__get_str(dev_name), __entry->status
 	)
 );
 
-- 
2.53.0

Re: [PATCH] ufs: core: tracing: Do not dereference pointers in TP_printk()

[Peter Wang (王信友)]

On Tue, 2026-06-30 at 18:54 -0400, Steven Rostedt wrote:
> From: Steven Rostedt <rostedt@goodmis.org>
> 
> The trace events in drivers/ufs/core/ufs_trace.h were converted to
> take a
> pointer to the hba structure as an argument for the tracepoint and
> then in
> TP_printk() the printing of the dev_name from the ring buffer was
> converted to using the dev dereferenced pointer from the hba saved
> pointer.
> 
> This is not allowed as the TP_printk() is executed at the time the
> trace
> event is read from /sys/kernel/tracing/trace file. That can happen
> literally, seconds, minutes, hours, weeks, days, or even months
> later!
> There is no guarantee that the hba pointer will still exist by the
> time it
> is dereferenced when the "trace" file is read.
> 
> Instead, save the device name from the hba pointer at the time the
> tracepoint is called and place it into the ring buffer event. Then
> the
> TP_printk() can read the name directly from the ring buffer and
> remove the
> possibility that it will read a freed pointer and crash the kernel.
> 
> This was detected when testing the trace event code that looks for
> TP_printk() parameters doing illegal derferences[1]
> 
> [1]
> https://lore.kernel.org/all/20260630184836.74d477b6@gandalf.local.home/
> 
> Cc: stable@vger.kernel.org
> Fixes: 583e518e71003 ("scsi: ufs: core: Add hba parameter to trace
> events")
> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

Reviewed-by: Peter Wang <peter.wang@mediatek.com>