s390/dis: Fix handling of format specifiers

The print_insn() function returns strings like "lghi %r1,0". To escape the
'%' character in sprintf() a second '%' is used. For example "lghi %%r1,0"
is converted into "lghi %r1,0".

After print_insn() the output string is passed to printk(). Because format
specifiers like "%r" or "%f" are ignored by printk() this works by chance
most of the time. But for instructions with control registers like
"lctl %c6,%c6,780" this fails because printk() interprets "%c" as
character format specifier.

Fix this problem and escape the '%' characters twice.

For example "lctl %%%%c6,%%%%c6,780" is then converted by sprintf()
into "lctl %%c6,%%c6,780" and by printk() into "lctl %c6,%c6,780".

Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Cc: stable@vger.kernel.org
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 12 insertions, 5 deletions

diff --git a/arch/s390/kernel/dis.c b/arch/s390/kernel/dis.c
index 8140d10c6785..6e72961608f0 100644
--- a/arch/s390/kernel/dis.c
+++ b/arch/s390/kernel/dis.c
@@ -1920,16 +1920,23 @@ static int print_insn(char *buffer, unsigned char *code, unsigned long addr)
                         }
                         if (separator)
                                 ptr += sprintf(ptr, "%c", separator);
+                        /*
+                         * Use four '%' characters below because of the
+                         * following two conversions:
+                         *
+                         *  1) sprintf: %%%%r -> %%r
+                         *  2) printk : %%r   -> %r
+                         */
                         if (operand->flags & OPERAND_GPR)
-                                ptr += sprintf(ptr, "%%r%i", value);
+                                ptr += sprintf(ptr, "%%%%r%i", value);
                         else if (operand->flags & OPERAND_FPR)
-                                ptr += sprintf(ptr, "%%f%i", value);
+                                ptr += sprintf(ptr, "%%%%f%i", value);
                         else if (operand->flags & OPERAND_AR)
-                                ptr += sprintf(ptr, "%%a%i", value);
+                                ptr += sprintf(ptr, "%%%%a%i", value);
                         else if (operand->flags & OPERAND_CR)
-                                ptr += sprintf(ptr, "%%c%i", value);
+                                ptr += sprintf(ptr, "%%%%c%i", value);
                         else if (operand->flags & OPERAND_VR)
-                                ptr += sprintf(ptr, "%%v%i", value);
+                                ptr += sprintf(ptr, "%%%%v%i", value);
                         else if (operand->flags & OPERAND_PCREL)
                                 ptr += sprintf(ptr, "%lx", (signed int) value
                                                                       + addr);