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| author | Thomas Gleixner <tglx@linutronix.de> | 2020-07-22 10:39:54 +0200 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2020-07-22 23:47:48 +0200 |
| commit | d181d2da0141371bbc360eaea78719203e165e1c (patch) | |
| tree | 4fe696be8b7938abbfa180a0dcef84e3c9616789 /arch/x86/kernel | |
| parent | 039a7a30ec102ec866d382a66f87f6f7654f8140 (diff) | |
| download | linux-d181d2da0141371bbc360eaea78719203e165e1c.tar.bz2 | |
x86/dumpstack: Dump user space code correctly again
H.J. reported that post 5.7 a segfault of a user space task does not longer
dump the Code bytes when /proc/sys/debug/exception-trace is enabled. It
prints 'Code: Bad RIP value.' instead.
This was broken by a recent change which made probe_kernel_read() reject
non-kernel addresses.
Update show_opcodes() so it retrieves user space opcodes via
copy_from_user_nmi().
Fixes: 98a23609b103 ("maccess: always use strict semantics for probe_kernel_read")
Reported-by: H.J. Lu <hjl.tools@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/87h7tz306w.fsf@nanos.tec.linutronix.de
Diffstat (limited to 'arch/x86/kernel')
| -rw-r--r-- | arch/x86/kernel/dumpstack.c | 27 |
1 files changed, 17 insertions, 10 deletions
diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c index b037cfa7c0c5..7401cc12c3cc 100644 --- a/arch/x86/kernel/dumpstack.c +++ b/arch/x86/kernel/dumpstack.c @@ -71,6 +71,22 @@ static void printk_stack_address(unsigned long address, int reliable, printk("%s %s%pB\n", log_lvl, reliable ? "" : "? ", (void *)address); } +static int copy_code(struct pt_regs *regs, u8 *buf, unsigned long src, + unsigned int nbytes) +{ + if (!user_mode(regs)) + return copy_from_kernel_nofault(buf, (u8 *)src, nbytes); + + /* + * Make sure userspace isn't trying to trick us into dumping kernel + * memory by pointing the userspace instruction pointer at it. + */ + if (__chk_range_not_ok(src, nbytes, TASK_SIZE_MAX)) + return -EINVAL; + + return copy_from_user_nmi(buf, (void __user *)src, nbytes); +} + /* * There are a couple of reasons for the 2/3rd prologue, courtesy of Linus: * @@ -97,17 +113,8 @@ void show_opcodes(struct pt_regs *regs, const char *loglvl) #define OPCODE_BUFSIZE (PROLOGUE_SIZE + 1 + EPILOGUE_SIZE) u8 opcodes[OPCODE_BUFSIZE]; unsigned long prologue = regs->ip - PROLOGUE_SIZE; - bool bad_ip; - - /* - * Make sure userspace isn't trying to trick us into dumping kernel - * memory by pointing the userspace instruction pointer at it. - */ - bad_ip = user_mode(regs) && - __chk_range_not_ok(prologue, OPCODE_BUFSIZE, TASK_SIZE_MAX); - if (bad_ip || copy_from_kernel_nofault(opcodes, (u8 *)prologue, - OPCODE_BUFSIZE)) { + if (copy_code(regs, opcodes, prologue, sizeof(opcodes))) { printk("%sCode: Bad RIP value.\n", loglvl); } else { printk("%sCode: %" __stringify(PROLOGUE_SIZE) "ph <%02x> %" |