| Message ID | 20240209192647.163042-4-rrichter@amd.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | None | expand |
On Fri, 9 Feb 2024 20:26:47 +0100 Robert Richter <rrichter@amd.com> wrote: > There exists card implementations with a CDAT table using a fix There exist ... fixed size buffer, > buffer, but with entries filled in that do not fill the whole table > length size. Then, the last entry in the CDAT table may not mark the > end of the CDAT table buffer specified by the length field in the CDAT > header. It can be shorter with trailing unused (zero'ed) data. The > actual table length is determined while reading all CDAT entries of > the table with DOE. > > If the table is greater than expected (containing zero'ed trailing > data), the CDAT parser fails with: > > [ 48.691717] Malformed DSMAS table length: (24:0) > [ 48.702084] [CDAT:0x00] Invalid zero length > [ 48.711460] cxl_port endpoint1: Failed to parse CDAT: -22 > > In addition, a check of the table buffer length is missing to prevent > an out-of-bound access then parsing the CDAT table. > > Hardening code against device returning borked table. Fix that by > providing an optional buffer length argument to > acpi_parse_entries_array() that can be used by cdat_table_parse() to > propagate the buffer size down to its users to check the buffer > length. This also prevents a possible out-of-bound access mentioned. > > Cc: "Rafael J. Wysocki" <rafael@kernel.org> > Cc: Len Brown <lenb@kernel.org> > Signed-off-by: Robert Richter <rrichter@amd.com> > Reviewed-by: Dave Jiang <dave.jiang@intel.com> I think we should scream a bit about this if we see it as I'm unconvinced the spec allows for an implementation like this. If the spec is unclear, lets seek a clarification. I'm fine with this as a defensive measure, I just don't want device vendors to keep doing it! Jonathan > --- > drivers/acpi/tables.c | 2 +- > drivers/cxl/core/cdat.c | 6 +++--- > include/linux/fw_table.h | 4 +++- > lib/fw_table.c | 15 ++++++++++----- > 4 files changed, 17 insertions(+), 10 deletions(-) > > diff --git a/drivers/acpi/tables.c b/drivers/acpi/tables.c > index b07f7d091d13..b976e5fc3fbc 100644 > --- a/drivers/acpi/tables.c > +++ b/drivers/acpi/tables.c > @@ -253,7 +253,7 @@ int __init_or_acpilib acpi_table_parse_entries_array( > > count = acpi_parse_entries_array(id, table_size, > (union fw_table_header *)table_header, > - proc, proc_num, max_entries); > + 0, proc, proc_num, max_entries); > > acpi_put_table(table_header); > return count; > diff --git a/drivers/cxl/core/cdat.c b/drivers/cxl/core/cdat.c > index 6fe11546889f..012d8f2a7945 100644 > --- a/drivers/cxl/core/cdat.c > +++ b/drivers/cxl/core/cdat.c > @@ -149,13 +149,13 @@ static int cxl_cdat_endpoint_process(struct cxl_port *port, > int rc; > > rc = cdat_table_parse(ACPI_CDAT_TYPE_DSMAS, cdat_dsmas_handler, > - dsmas_xa, port->cdat.table); > + dsmas_xa, port->cdat.table, port->cdat.length); > rc = cdat_table_parse_output(rc); > if (rc) > return rc; > > rc = cdat_table_parse(ACPI_CDAT_TYPE_DSLBIS, cdat_dslbis_handler, > - dsmas_xa, port->cdat.table); > + dsmas_xa, port->cdat.table, port->cdat.length); > return cdat_table_parse_output(rc); > } > > @@ -511,7 +511,7 @@ void cxl_switch_parse_cdat(struct cxl_port *port) > return; > > rc = cdat_table_parse(ACPI_CDAT_TYPE_SSLBIS, cdat_sslbis_handler, > - port, port->cdat.table); > + port, port->cdat.table, port->cdat.length); > rc = cdat_table_parse_output(rc); > if (rc) > dev_dbg(&port->dev, "Failed to parse SSLBIS: %d\n", rc); > diff --git a/include/linux/fw_table.h b/include/linux/fw_table.h > index 95421860397a..3ff4c277296f 100644 > --- a/include/linux/fw_table.h > +++ b/include/linux/fw_table.h > @@ -40,12 +40,14 @@ union acpi_subtable_headers { > > int acpi_parse_entries_array(char *id, unsigned long table_size, > union fw_table_header *table_header, > + unsigned long max_length, > struct acpi_subtable_proc *proc, > int proc_num, unsigned int max_entries); > > int cdat_table_parse(enum acpi_cdat_type type, > acpi_tbl_entry_handler_arg handler_arg, void *arg, > - struct acpi_table_cdat *table_header); > + struct acpi_table_cdat *table_header, > + unsigned long length); > > /* CXL is the only non-ACPI consumer of the FIRMWARE_TABLE library */ > #if IS_ENABLED(CONFIG_ACPI) && !IS_ENABLED(CONFIG_CXL_BUS) > diff --git a/lib/fw_table.c b/lib/fw_table.c > index c3569d2ba503..16291814450e 100644 > --- a/lib/fw_table.c > +++ b/lib/fw_table.c > @@ -127,6 +127,7 @@ static __init_or_fwtbl_lib int call_handler(struct acpi_subtable_proc *proc, > * > * @id: table id (for debugging purposes) > * @table_size: size of the root table > + * @max_length: maximum size of the table (ignore if 0) > * @table_header: where does the table start? > * @proc: array of acpi_subtable_proc struct containing entry id > * and associated handler with it > @@ -148,18 +149,21 @@ static __init_or_fwtbl_lib int call_handler(struct acpi_subtable_proc *proc, > int __init_or_fwtbl_lib > acpi_parse_entries_array(char *id, unsigned long table_size, > union fw_table_header *table_header, > + unsigned long max_length, > struct acpi_subtable_proc *proc, > int proc_num, unsigned int max_entries) > { > - unsigned long table_end, subtable_len, entry_len; > + unsigned long table_len, table_end, subtable_len, entry_len; > struct acpi_subtable_entry entry; > enum acpi_subtable_type type; > int count = 0; > int i; > > type = acpi_get_subtable_type(id); > - table_end = (unsigned long)table_header + > - acpi_table_get_length(type, table_header); > + table_len = acpi_table_get_length(type, table_header); > + if (max_length && max_length < table_len) > + table_len = max_length; if (max_length) table_len = min(max_length, table_len); > + table_end = (unsigned long)table_header + table_len; > > /* Parse all entries looking for a match. */ > > @@ -208,7 +212,8 @@ int __init_or_fwtbl_lib > cdat_table_parse(enum acpi_cdat_type type, > acpi_tbl_entry_handler_arg handler_arg, > void *arg, > - struct acpi_table_cdat *table_header) > + struct acpi_table_cdat *table_header, > + unsigned long length) > { > struct acpi_subtable_proc proc = { > .id = type, > @@ -222,6 +227,6 @@ cdat_table_parse(enum acpi_cdat_type type, > return acpi_parse_entries_array(ACPI_SIG_CDAT, > sizeof(struct acpi_table_cdat), > (union fw_table_header *)table_header, > - &proc, 1, 0); > + length, &proc, 1, 0); > } > EXPORT_SYMBOL_FWTBL_LIB(cdat_table_parse);
On 14.02.24 17:44:44, Jonathan Cameron wrote: > On Wed, 14 Feb 2024 17:39:27 +0000 > Jonathan Cameron <Jonathan.Cameron@Huawei.com> wrote: > > > On Fri, 9 Feb 2024 20:26:47 +0100 > > Robert Richter <rrichter@amd.com> wrote: > > > > > There exists card implementations with a CDAT table using a fix > > There exist ... fixed size buffer, > > > buffer, but with entries filled in that do not fill the whole table > > > length size. Then, the last entry in the CDAT table may not mark the > > > end of the CDAT table buffer specified by the length field in the CDAT > > > header. It can be shorter with trailing unused (zero'ed) data. The > > > actual table length is determined while reading all CDAT entries of > > > the table with DOE. > > > > > > If the table is greater than expected (containing zero'ed trailing > > > data), the CDAT parser fails with: > > > > > > [ 48.691717] Malformed DSMAS table length: (24:0) > > > [ 48.702084] [CDAT:0x00] Invalid zero length > > > [ 48.711460] cxl_port endpoint1: Failed to parse CDAT: -22 > > > > > > In addition, a check of the table buffer length is missing to prevent > > > an out-of-bound access then parsing the CDAT table. > > > > > > Hardening code against device returning borked table. Fix that by > > > providing an optional buffer length argument to > > > acpi_parse_entries_array() that can be used by cdat_table_parse() to > > > propagate the buffer size down to its users to check the buffer > > > length. This also prevents a possible out-of-bound access mentioned. > > > > > > Cc: "Rafael J. Wysocki" <rafael@kernel.org> > > > Cc: Len Brown <lenb@kernel.org> > > > Signed-off-by: Robert Richter <rrichter@amd.com> > > > Reviewed-by: Dave Jiang <dave.jiang@intel.com> > > > > I think we should scream a bit about this if we see it > > as I'm unconvinced the spec allows for an implementation like this. > > > > If the spec is unclear, lets seek a clarification. > > > > I'm fine with this as a defensive measure, I just don't want > > device vendors to keep doing it! > > > Scrub that - I got around to checking the CDAT spec. It can > change length whilst we are reading it due to DSEMTS entry > counts being allowed to change. > https://uefi.org/sites/default/files/resources/Coherent%20Device%20Attribute%20Table_1.03.pdf > (it's in the description of the Sequence field) > > Sure we'll notice that the checksum fails and the sequence number > has updated but that doesn't help us if we went out of bounds > before we knew that. > > Definitely good to check this as I think we can hit it even > if we don't have a potentially buggy device. > I'd still like to moan if we get inconsistent sizes and it > isn't a race though. Can we find a clean way to detect this > at a point where we know we have a valid complete table? I will add a warning about a length mismatch. Thanks, -Robert
diff --git a/drivers/acpi/tables.c b/drivers/acpi/tables.c index b07f7d091d13..b976e5fc3fbc 100644 --- a/drivers/acpi/tables.c +++ b/drivers/acpi/tables.c @@ -253,7 +253,7 @@ int __init_or_acpilib acpi_table_parse_entries_array( count = acpi_parse_entries_array(id, table_size, (union fw_table_header *)table_header, - proc, proc_num, max_entries); + 0, proc, proc_num, max_entries); acpi_put_table(table_header); return count; diff --git a/drivers/cxl/core/cdat.c b/drivers/cxl/core/cdat.c index 6fe11546889f..012d8f2a7945 100644 --- a/drivers/cxl/core/cdat.c +++ b/drivers/cxl/core/cdat.c @@ -149,13 +149,13 @@ static int cxl_cdat_endpoint_process(struct cxl_port *port, int rc; rc = cdat_table_parse(ACPI_CDAT_TYPE_DSMAS, cdat_dsmas_handler, - dsmas_xa, port->cdat.table); + dsmas_xa, port->cdat.table, port->cdat.length); rc = cdat_table_parse_output(rc); if (rc) return rc; rc = cdat_table_parse(ACPI_CDAT_TYPE_DSLBIS, cdat_dslbis_handler, - dsmas_xa, port->cdat.table); + dsmas_xa, port->cdat.table, port->cdat.length); return cdat_table_parse_output(rc); } @@ -511,7 +511,7 @@ void cxl_switch_parse_cdat(struct cxl_port *port) return; rc = cdat_table_parse(ACPI_CDAT_TYPE_SSLBIS, cdat_sslbis_handler, - port, port->cdat.table); + port, port->cdat.table, port->cdat.length); rc = cdat_table_parse_output(rc); if (rc) dev_dbg(&port->dev, "Failed to parse SSLBIS: %d\n", rc); diff --git a/include/linux/fw_table.h b/include/linux/fw_table.h index 95421860397a..3ff4c277296f 100644 --- a/include/linux/fw_table.h +++ b/include/linux/fw_table.h @@ -40,12 +40,14 @@ union acpi_subtable_headers { int acpi_parse_entries_array(char *id, unsigned long table_size, union fw_table_header *table_header, + unsigned long max_length, struct acpi_subtable_proc *proc, int proc_num, unsigned int max_entries); int cdat_table_parse(enum acpi_cdat_type type, acpi_tbl_entry_handler_arg handler_arg, void *arg, - struct acpi_table_cdat *table_header); + struct acpi_table_cdat *table_header, + unsigned long length); /* CXL is the only non-ACPI consumer of the FIRMWARE_TABLE library */ #if IS_ENABLED(CONFIG_ACPI) && !IS_ENABLED(CONFIG_CXL_BUS) diff --git a/lib/fw_table.c b/lib/fw_table.c index c3569d2ba503..16291814450e 100644 --- a/lib/fw_table.c +++ b/lib/fw_table.c @@ -127,6 +127,7 @@ static __init_or_fwtbl_lib int call_handler(struct acpi_subtable_proc *proc, * * @id: table id (for debugging purposes) * @table_size: size of the root table + * @max_length: maximum size of the table (ignore if 0) * @table_header: where does the table start? * @proc: array of acpi_subtable_proc struct containing entry id * and associated handler with it @@ -148,18 +149,21 @@ static __init_or_fwtbl_lib int call_handler(struct acpi_subtable_proc *proc, int __init_or_fwtbl_lib acpi_parse_entries_array(char *id, unsigned long table_size, union fw_table_header *table_header, + unsigned long max_length, struct acpi_subtable_proc *proc, int proc_num, unsigned int max_entries) { - unsigned long table_end, subtable_len, entry_len; + unsigned long table_len, table_end, subtable_len, entry_len; struct acpi_subtable_entry entry; enum acpi_subtable_type type; int count = 0; int i; type = acpi_get_subtable_type(id); - table_end = (unsigned long)table_header + - acpi_table_get_length(type, table_header); + table_len = acpi_table_get_length(type, table_header); + if (max_length && max_length < table_len) + table_len = max_length; + table_end = (unsigned long)table_header + table_len; /* Parse all entries looking for a match. */ @@ -208,7 +212,8 @@ int __init_or_fwtbl_lib cdat_table_parse(enum acpi_cdat_type type, acpi_tbl_entry_handler_arg handler_arg, void *arg, - struct acpi_table_cdat *table_header) + struct acpi_table_cdat *table_header, + unsigned long length) { struct acpi_subtable_proc proc = { .id = type, @@ -222,6 +227,6 @@ cdat_table_parse(enum acpi_cdat_type type, return acpi_parse_entries_array(ACPI_SIG_CDAT, sizeof(struct acpi_table_cdat), (union fw_table_header *)table_header, - &proc, 1, 0); + length, &proc, 1, 0); } EXPORT_SYMBOL_FWTBL_LIB(cdat_table_parse);