Re: [PATCH v4 1/3] RAS: Fix inverted context info bounds check in ARM processor errors

Re: [PATCH v4 1/3] RAS: Fix inverted context info bounds check in ARM processor errors

[Liuwenliang (Abbott Liu)]

Hi Hanjun,

Thank you for the review.

On 2026/9/17 10:13, Hanjun Guo wrote:
> On 2026/9/9 19:28, Abbott Liu wrote:
> > Commit 87880af2d24e ("APEI/GHES: ARM processor Error: don't go past
> > allocated memory") added bounds checks for malformed ARM processor
> > error records but contained a bug:
> >
> >    In log_arm_hw_error(), the ctx_info bounds check is inverted. The
> >    condition "sz + (long)ctx_info - (long)err >= err->section_length"
> >    adds ctx_info->size when the context header is already past the end
> >    of the section instead of when it is within bounds. So change the
> >    comparison to <=.
> >
> > Fixes: 87880af2d24e ("APEI/GHES: ARM processor Error: don't go past allocated memory")
> > Signed-off-by: Abbott Liu <liuwenliang@huawei.com>
> > ---
> >   drivers/ras/ras.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/ras/ras.c b/drivers/ras/ras.c
> > index 03df3db62334..2540538a16a8 100644
> > --- a/drivers/ras/ras.c
> > +++ b/drivers/ras/ras.c
> > @@ -74,7 +74,7 @@ void log_arm_hw_error(struct cper_sec_proc_arm *err, const u8 sev)
> >   	for (n = 0; n < err->context_info_num; n++) {
> >   		sz = sizeof(struct cper_arm_ctx_info);
> >
> > -		if (sz + (long)ctx_info - (long)err >= err->section_length)
> > +		if (sz + (long)ctx_info - (long)err <= err->section_length)
> >   			sz += ctx_info->size;
> >
> >   		ctx_info = (struct cper_arm_ctx_info *)((long)ctx_info + sz);
> >
>
> Reviewed-by: Hanjun Guo <guohanjun@huawei.com>

Thanks, I will add your Reviewed-by tag in v5, there will be no code changes in
that version, so the tag remains valid.

>
> Thanks
> Hanjun

[PATCH v4 0/3] RAS: Fix ARM processor error bounds checking

[Abbott Liu]

Commit 87880af2d24e ("APEI/GHES: ARM processor Error: don't go past
allocated memory") and commit 05954511b73e ("RAS: Report all ARM
processor CPER information to userspace") introduced bounds checking
for malformed ARM processor error records in log_arm_hw_error().
However, three issues remain:

1. The ctx_info bounds check condition is inverted: it adds
   ctx_info->size when the context header is already past the end of
   the section instead of when it is within bounds.

2. When vsei_len < 0, the error path does not verify pei_len and
   ctx_len. Since these are derived from err_info_num and
   context_info_num, they may describe regions beyond the allocated
   record, causing trace_arm_event() to read out of bounds.

3. ctx_info->size is a u32 taken directly from the firmware-generated
   record. A value over 0x7fffffff overflows the signed int sz used
   to advance ctx_info, so the iteration can walk past the end of the
   section.

Patch 1 fixes the inverted bounds check for context info iteration.
Patch 2 sanitizes pei_len/ctx_len/ven_err_data in the vsei_len < 0
error path to prevent out-of-bounds reads in trace_arm_event().
Patch 3 checks each context entry with 64-bit arithmetic so that both
the header and the context data fit in the section, and stops the walk
at the first entry that does not fit, so a malformed size cannot
overflow sz and walk ctx_info out of the section.

Changes in v4:
  - Remove the empty line between the Fixes: and Signed-off-by: tags
    in patches 1 and 2, per Hanjun Guo's comments.
  - Add braces around the else branch that assigns ven_err_data in
    patch 2, as suggested by Hanjun Guo.
  - Add new patch 3 to check each context entry with 64-bit
    arithmetic and stop the walk at the first entry that does not fit
    in the section, so a ctx_info->size over 0x7fffffff cannot
    overflow the signed int sz and walk ctx_info past the section,
    addressing Hanjun Guo's overflow comment.

Changes in v3:
  - There was no change, and the email was sent by mistake.

Changes in v2:
  - Split the original single patch into two separate patches, one
    for each distinct fix, to ease review and backporting.

v2:
  RAS: Fix ARM processor error bounds checking
  https://lore.kernel.org/all/20260825134323.4181892-1-liuwenliang@huawei.com/

v1:
  RAS: Fix out-of-range section_length in ARM processor error handling
  https://lore.kernel.org/all/20260820131829.1006371-1-liuwenliang@huawei.com/

Abbott Liu (3):
  RAS: Fix inverted context info bounds check in ARM processor errors
  RAS: Fix out-of-bounds read when tracing arm_event
  RAS: Fix integer overflow in ARM processor error context walk

 drivers/ras/ras.c | 33 +++++++++++++++++++++++++++------
 1 file changed, 27 insertions(+), 6 deletions(-)

-- 
2.43.0

[PATCH v4 1/3] RAS: Fix inverted context info bounds check in ARM processor errors

[Abbott Liu]

Commit 87880af2d24e ("APEI/GHES: ARM processor Error: don't go past
allocated memory") added bounds checks for malformed ARM processor
error records but contained a bug:

  In log_arm_hw_error(), the ctx_info bounds check is inverted. The
  condition "sz + (long)ctx_info - (long)err >= err->section_length"
  adds ctx_info->size when the context header is already past the end
  of the section instead of when it is within bounds. So change the
  comparison to <=.

Fixes: 87880af2d24e ("APEI/GHES: ARM processor Error: don't go past allocated memory")
Signed-off-by: Abbott Liu <liuwenliang@huawei.com>
---
 drivers/ras/ras.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/ras/ras.c b/drivers/ras/ras.c
index 03df3db62334..2540538a16a8 100644
--- a/drivers/ras/ras.c
+++ b/drivers/ras/ras.c
@@ -74,7 +74,7 @@ void log_arm_hw_error(struct cper_sec_proc_arm *err, const u8 sev)
 	for (n = 0; n < err->context_info_num; n++) {
 		sz = sizeof(struct cper_arm_ctx_info);
 
-		if (sz + (long)ctx_info - (long)err >= err->section_length)
+		if (sz + (long)ctx_info - (long)err <= err->section_length)
 			sz += ctx_info->size;
 
 		ctx_info = (struct cper_arm_ctx_info *)((long)ctx_info + sz);
-- 
2.43.0

Re: [PATCH v4 1/3] RAS: Fix inverted context info bounds check in ARM processor errors

[Hanjun Guo]

On 2026/9/9 19:28, Abbott Liu wrote:
> Commit 87880af2d24e ("APEI/GHES: ARM processor Error: don't go past
> allocated memory") added bounds checks for malformed ARM processor
> error records but contained a bug:
> 
>    In log_arm_hw_error(), the ctx_info bounds check is inverted. The
>    condition "sz + (long)ctx_info - (long)err >= err->section_length"
>    adds ctx_info->size when the context header is already past the end
>    of the section instead of when it is within bounds. So change the
>    comparison to <=.
> 
> Fixes: 87880af2d24e ("APEI/GHES: ARM processor Error: don't go past allocated memory")
> Signed-off-by: Abbott Liu <liuwenliang@huawei.com>
> ---
>   drivers/ras/ras.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/ras/ras.c b/drivers/ras/ras.c
> index 03df3db62334..2540538a16a8 100644
> --- a/drivers/ras/ras.c
> +++ b/drivers/ras/ras.c
> @@ -74,7 +74,7 @@ void log_arm_hw_error(struct cper_sec_proc_arm *err, const u8 sev)
>   	for (n = 0; n < err->context_info_num; n++) {
>   		sz = sizeof(struct cper_arm_ctx_info);
>   
> -		if (sz + (long)ctx_info - (long)err >= err->section_length)
> +		if (sz + (long)ctx_info - (long)err <= err->section_length)
>   			sz += ctx_info->size;
>   
>   		ctx_info = (struct cper_arm_ctx_info *)((long)ctx_info + sz);
> 

Reviewed-by: Hanjun Guo <guohanjun@huawei.com>

Thanks
Hanjun