Re: [PATCH v3] ACPI: pfr_update: fix stack buffer overflow in query_capability()

Hi, just gently nudging this. Thanks!


From: Anirudh Prasad <[email protected]>
To: "linux-acpi"<[email protected]>
Cc: "rafaeljwysocki"<[email protected]>, "linux-kernel"<[email protected]>, "stable"<[email protected]>
Date: Fri, 07 Aug 2026 21:31:12 +0530
Subject: [PATCH v3] ACPI: pfr_update: fix stack buffer overflow in query_capability()

 > query_capability() copies four ACPI buffer objects returned by the 
 > firmware _DSM into fixed-size u8[16] fields in struct 
 > pfru_update_cap_info using memcpy with the firmware-supplied length: 
 >  
 >  memcpy(&cap_hdr->code_type, 
 >  elements[CAP_CODE_TYPE_IDX].buffer.pointer, 
 >  elements[CAP_CODE_TYPE_IDX].buffer.length); 
 >  
 > The same pattern repeats for drv_type, platform_id, and oem_id. 
 > If the firmware returns buffer.length > 16 for any of these fields, 
 > memcpy writes past the destination array. 
 >  
 > struct pfru_update_cap_info is stack-allocated in pfru_ioctl(). 
 > Confirmed with KASAN on 7.2-rc6: three stack-out-of-bounds reports 
 > are generated when a DSM returns 64-byte buffers, with writes reaching 
 > 44 bytes past the end of cap_hdr's [64, 156) frame window into 
 > adjacent stack redzones. 
 >  
 > Introduce a helper pointer to out_obj->package.elements and use it 
 > to validate each buffer length against its destination field size 
 > before copying, returning -EINVAL if the firmware supplies an 
 > oversized buffer. 
 >  
 > Fixes: 0db89fa243e5 ("ACPI: Introduce Platform Firmware Runtime Update device driver") 
 > Cc: [email protected] 
 > Signed-off-by: Anirudh Prasad <[email protected]> 
 > --- 
 >  drivers/acpi/pfr_update.c | 47 ++++++++++++++++++++++----------------- 
 >  1 file changed, 26 insertions(+), 21 deletions(-) 
 >  
 > diff --git a/drivers/acpi/pfr_update.c b/drivers/acpi/pfr_update.c 
 > index 6283105bb0e8..79cedd4cf2a2 100644 
 > --- a/drivers/acpi/pfr_update.c 
 > +++ b/drivers/acpi/pfr_update.c 
 > @@ -120,7 +120,7 @@ static int query_capability(struct pfru_update_cap_info *cap_hdr, 
 >                  struct pfru_device *pfru_dev) 
 >  { 
 >      acpi_handle handle = ACPI_HANDLE(pfru_dev->parent_dev); 
 > -    union acpi_object *out_obj; 
 > +    union acpi_object *out_obj, *elem; 
 >      int ret = -EINVAL; 
 >  
 >      out_obj = acpi_evaluate_dsm_typed(handle, &pfru_guid, 
 > @@ -150,7 +150,9 @@ static int query_capability(struct pfru_update_cap_info *cap_hdr, 
 >          goto free_acpi_buffer; 
 >      } 
 >  
 > -    cap_hdr->status = out_obj->package.elements[CAP_STATUS_IDX].integer.value; 
 > +    elem = out_obj->package.elements; 
 > + 
 > +    cap_hdr->status = elem[CAP_STATUS_IDX].integer.value; 
 >      if (cap_hdr->status != DSM_SUCCEED) { 
 >          ret = -EBUSY; 
 >          dev_dbg(pfru_dev->parent_dev, "Query cap Error Status:%d\n", 
 > @@ -158,29 +160,32 @@ static int query_capability(struct pfru_update_cap_info *cap_hdr, 
 >          goto free_acpi_buffer; 
 >      } 
 >  
 > -    cap_hdr->update_cap = out_obj->package.elements[CAP_UPDATE_IDX].integer.value; 
 > +    if (elem[CAP_CODE_TYPE_IDX].buffer.length > sizeof(cap_hdr->code_type) || 
 > +        elem[CAP_DRV_TYPE_IDX].buffer.length > sizeof(cap_hdr->drv_type) || 
 > +        elem[CAP_PLAT_ID_IDX].buffer.length > sizeof(cap_hdr->platform_id) || 
 > +        elem[CAP_OEM_ID_IDX].buffer.length > sizeof(cap_hdr->oem_id)) { 
 > +        ret = -EINVAL; 
 > +        goto free_acpi_buffer; 
 > +    } 
 > + 
 > +    cap_hdr->update_cap = elem[CAP_UPDATE_IDX].integer.value; 
 >      memcpy(&cap_hdr->code_type, 
 > -           out_obj->package.elements[CAP_CODE_TYPE_IDX].buffer.pointer, 
 > -           out_obj->package.elements[CAP_CODE_TYPE_IDX].buffer.length); 
 > -    cap_hdr->fw_version = 
 > -        out_obj->package.elements[CAP_FW_VER_IDX].integer.value; 
 > -    cap_hdr->code_rt_version = 
 > -        out_obj->package.elements[CAP_CODE_RT_VER_IDX].integer.value; 
 > +           elem[CAP_CODE_TYPE_IDX].buffer.pointer, 
 > +           elem[CAP_CODE_TYPE_IDX].buffer.length); 
 > +    cap_hdr->fw_version = elem[CAP_FW_VER_IDX].integer.value; 
 > +    cap_hdr->code_rt_version = elem[CAP_CODE_RT_VER_IDX].integer.value; 
 >      memcpy(&cap_hdr->drv_type, 
 > -           out_obj->package.elements[CAP_DRV_TYPE_IDX].buffer.pointer, 
 > -           out_obj->package.elements[CAP_DRV_TYPE_IDX].buffer.length); 
 > -    cap_hdr->drv_rt_version = 
 > -        out_obj->package.elements[CAP_DRV_RT_VER_IDX].integer.value; 
 > -    cap_hdr->drv_svn = 
 > -        out_obj->package.elements[CAP_DRV_SVN_IDX].integer.value; 
 > +           elem[CAP_DRV_TYPE_IDX].buffer.pointer, 
 > +           elem[CAP_DRV_TYPE_IDX].buffer.length); 
 > +    cap_hdr->drv_rt_version = elem[CAP_DRV_RT_VER_IDX].integer.value; 
 > +    cap_hdr->drv_svn = elem[CAP_DRV_SVN_IDX].integer.value; 
 >      memcpy(&cap_hdr->platform_id, 
 > -           out_obj->package.elements[CAP_PLAT_ID_IDX].buffer.pointer, 
 > -           out_obj->package.elements[CAP_PLAT_ID_IDX].buffer.length); 
 > +           elem[CAP_PLAT_ID_IDX].buffer.pointer, 
 > +           elem[CAP_PLAT_ID_IDX].buffer.length); 
 >      memcpy(&cap_hdr->oem_id, 
 > -           out_obj->package.elements[CAP_OEM_ID_IDX].buffer.pointer, 
 > -           out_obj->package.elements[CAP_OEM_ID_IDX].buffer.length); 
 > -    cap_hdr->oem_info_len = 
 > -        out_obj->package.elements[CAP_OEM_INFO_IDX].buffer.length; 
 > +           elem[CAP_OEM_ID_IDX].buffer.pointer, 
 > +           elem[CAP_OEM_ID_IDX].buffer.length); 
 > +    cap_hdr->oem_info_len = elem[CAP_OEM_INFO_IDX].buffer.length; 
 >  
 >      ret = 0; 
 >  
 > -- 
 > 2.55.0 
 >  
 >