[PATCH v3 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 v3:
  - 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 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@xxxxxxxxxx/

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

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