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ACPI/APEI: Limit printable size of BERT table data #1
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Check that the length recorded in the generic error status block is within the region before checking the contents of the region itself. Otherwise it may result in an out-of-bounds access if the system firmware has generated a status block with an invalid length (larger than the mapped region). Also move the block_status check so that it only happens after the block has been verified to be within the mapped region. Signed-off-by: Ross Lagerwall <[email protected]> Acked-by: Borislav Petkov <[email protected]> Tested-by: Tyler Baicar <[email protected]> Signed-off-by: Rafael J. Wysocki <[email protected]> (cherry picked from commit 1c0d9b1c31d19d3aa90296a184e4624545d7d1ee)
Platforms with large BERT table data can trigger soft lockup errors while attempting to print the entire BERT table data to the console at boot: watchdog: BUG: soft lockup - CPU#160 stuck for 23s! [swapper/0:1] Observed on Ampere Altra systems with a single BERT record of ~250KB. The original bert driver appears to have assumed relatively small table data. Since it is impractical to reassemble large table data from interwoven console messages, and the table data is available in /sys/firmware/acpi/tables/data/BERT limit the size for tables printed to the console to 1024 (for no reason other than it seemed like a good place to kick off the discussion, would appreciate feedback from existing users in terms of what size would maintain their current usage model). Alternatively, we could make printing a CONFIG option, use the bert_disable boot arg (or something similar), or use a debug log level. However, all those solutions require extra steps or change the existing behavior for small table data. Limiting the size preserves existing behavior on existing platforms with small table data, and eliminates the soft lockups for platforms with large table data, while still making it available. Signed-off-by: Darren Hart <[email protected]> Signed-off-by: Rafael J. Wysocki <[email protected]> (cherry picked from commit 3f8dec116210ca649163574ed5f8df1e3b837d07)
The fix in commit 3f8dec116210 ("ACPI/APEI: Limit printable size of BERT
table data") does not work as intended on systems where the BIOS has a
fixed size block of memory for the BERT table, relying on s/w to quit
when it finds a record with estatus->block_status == 0. On these systems
all errors are suppressed because the check:
if (region_len < ACPI_BERT_PRINT_MAX_LEN)
always fails.
New scheme skips individual CPER records that are too large, and also
limits the total number of records that will be printed to 5.
Fixes: 3f8dec116210 ("ACPI/APEI: Limit printable size of BERT table data")
Cc: All applicable <[email protected]>
Signed-off-by: Tony Luck <[email protected]>
Signed-off-by: Rafael J. Wysocki <[email protected]>
(cherry picked from commit c3481b6b75b4797657838f44028fd28226ab48e0)
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Platforms with large BERT table data can trigger soft lockup errors
while attempting to print the entire BERT table data to the console at
boot:
watchdog: BUG: soft lockup - CPU#160 stuck for 23s! [swapper/0:1]
Observed on Ampere Altra systems with a single BERT record of ~250KB.
The original bert driver appears to have assumed relatively small table
data. Since it is impractical to reassemble large table data from
interwoven console messages, and the table data is available in
/sys/firmware/acpi/tables/data/BERT
limit the size for tables printed to the console to 1024 (for no reason
other than it seemed like a good place to kick off the discussion, would
appreciate feedback from existing users in terms of what size would
maintain their current usage model).
Alternatively, we could make printing a CONFIG option, use the
bert_disable boot arg (or something similar), or use a debug log level.
However, all those solutions require extra steps or change the existing
behavior for small table data. Limiting the size preserves existing
behavior on existing platforms with small table data, and eliminates the
soft lockups for platforms with large table data, while still making it
available.
Signed-off-by: Darren Hart [email protected]
Signed-off-by: Rafael J. Wysocki [email protected]
(cherry picked from commit 3f8dec116210ca649163574ed5f8df1e3b837d07)