[PATCH 4.9 154/264] random: round-robin registers as ulong, not u32

Greg Kroah-Hartman
2022-06-23T17:01:17Z

From: "Jason A. Donenfeld" <Jason@zx2c4.com>

commit da3951ebdcd1cb1d5c750e08cd05aee7b0c04d9a upstream.

When the interrupt handler does not have a valid cycle counter, it calls
get_reg() to read a register from the irq stack, in round-robin.
Currently it does this assuming that registers are 32-bit. This is
_probably_ the case, and probably all platforms without cycle counters
are in fact 32-bit platforms. But maybe not, and either way, it's not
quite correct. This commit fixes that to deal with `unsigned long`
rather than `u32`.

Cc: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/char/random.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1257,15 +1257,15 @@ int random_online_cpu(unsigned int cpu)
}
#endif

-static u32 get_reg(struct fast_pool *f, struct pt_regs *regs)
+static unsigned long get_reg(struct fast_pool *f, struct pt_regs *regs)
{
- u32 *ptr = (u32 *)regs;
+ unsigned long *ptr = (unsigned long *)regs;
unsigned int idx;

if (regs == NULL)
return 0;
idx = READ_ONCE(f->reg_idx);
- if (idx >= sizeof(struct pt_regs) / sizeof(u32))
+ if (idx >= sizeof(struct pt_regs) / sizeof(unsigned long))
idx = 0;
ptr += idx++;
WRITE_ONCE(f->reg_idx, idx);