From 62165600ae73ebd76e2d9b992b36360408d570d8 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (VMware)" Date: Fri, 5 Oct 2018 10:08:03 -0400 Subject: [PATCH] vsprintf: Fix off-by-one bug in bstr_printf() processing dereferenced pointers The functions vbin_printf() and bstr_printf() are used by trace_printk() to try to keep the overhead down during printing. trace_printk() uses vbin_printf() at the time of execution, as it only scans the fmt string to record the printf values into the buffer, and then uses vbin_printf() to do the conversions to print the string based on the format and the saved values in the buffer. This is an issue for dereferenced pointers, as before commit 841a915d20c7b, the processing of the pointer could happen some time after the pointer value was recorded (reading the trace buffer). This means the processing of the value at a later time could show different results, or even crash the system, if the pointer no longer existed. Commit 841a915d20c7b addressed this by processing dereferenced pointers at the time of execution and save the result in the ring buffer as a string. The bstr_printf() would then treat these pointers as normal strings, and print the value. But there was an off-by-one bug here, where after processing the argument, it move the pointer only "strlen(arg)" which made the arg pointer not point to the next argument in the ring buffer, but instead point to the nul character of the last argument. This causes any values after a dereferenced pointer to be corrupted. Cc: stable@vger.kernel.org Fixes: 841a915d20c7b ("vsprintf: Do not have bprintf dereference pointers") Reported-by: Nikolay Borisov Tested-by: Nikolay Borisov Signed-off-by: Steven Rostedt (VMware) --- lib/vsprintf.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/lib/vsprintf.c b/lib/vsprintf.c index d5b3a3f95c01..812e59e13fe6 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -2794,7 +2794,7 @@ int bstr_printf(char *buf, size_t size, const char *fmt, const u32 *bin_buf) copy = end - str; memcpy(str, args, copy); str += len; - args += len; + args += len + 1; } } if (process) -- 2.39.5