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powerpc/pseries: Avoid using the size greater than RTAS_ERROR_LOG_MAX. 

The global mce data buffer that used to copy rtas error log is of 2048
(RTAS_ERROR_LOG_MAX) bytes in size. Before the copy we read
extended_log_length from rtas error log header, then use max of
extended_log_length and RTAS_ERROR_LOG_MAX as a size of data to be copied.
Ideally the platform (phyp) will never send extended error log with
size > 2048. But if that happens, then we have a risk of buffer overrun
and corruption. Fix this by using min_t instead.

Fixes: d368514c30 ("powerpc: Fix corruption when grabbing FWNMI data")
Reported-by: Michal Suchanek <msuchanek@suse.com>
Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Mahesh Salgaonkar 2018-07-04 23:27:02 +05:30 committed by Michael Ellerman
parent e27e0a9465
commit 74e96bf44f
1 changed files with 1 additions and 1 deletions
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arch/powerpc/platforms/pseries/ras.c
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@ -371,7 +371,7 @@ static struct rtas_error_log *fwnmi_get_errinfo(struct pt_regs *regs)
int len, error_log_length; int len, error_log_length;
error_log_length = 8 + rtas_error_extended_log_length(h); error_log_length = 8 + rtas_error_extended_log_length(h);
len = max_t(int, error_log_length, RTAS_ERROR_LOG_MAX); len = min_t(int, error_log_length, RTAS_ERROR_LOG_MAX);
memset(global_mce_data_buf, 0, RTAS_ERROR_LOG_MAX); memset(global_mce_data_buf, 0, RTAS_ERROR_LOG_MAX);
memcpy(global_mce_data_buf, h, len); memcpy(global_mce_data_buf, h, len);
errhdr = (struct rtas_error_log *)global_mce_data_buf; errhdr = (struct rtas_error_log *)global_mce_data_buf;