From 78004e9a87f240df03e2f73120d291763c32e0a7 Mon Sep 17 00:00:00 2001 From: Ali Ahmet Memis Date: Fri, 21 Aug 2026 01:45:27 +0000 Subject: openrisc: fix arbitrary kernel memory access via or1k_atomic syscall sys_or1k_atomic() (syscall 244 in the "or1k" ABI) takes two user pointers, v1 and v2, and swaps the words they point to in hand-written assembly. l.lwz r29,0(r4) l.lwz r27,0(r5) l.sw 0(r4),r27 l.sw 0(r5),r29 The pointers are not checked with access_ok(). The four memory accesses also have no exception table entries. A caller passes a kernel address as either pointer, and the syscall reads from and writes to it directly. This gives an unprivileged process a kernel read/write primitive. It overwrites kernel data such as the sys_call_table, gaining code execution in kernel context. Check both pointers before entering the critical section. Add fixups for the four memory accesses so faults on valid but unmapped user addresses return -EFAULT. [shorne@gmail.com: fix comment style] Fixes: 9d02a4283e9c ("OpenRISC: Boot code") Cc: stable@vger.kernel.org Signed-off-by: Ali Ahmet Memis Signed-off-by: Stafford Horne --- drivers/clocksource/mmio.c | 75 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 75 insertions(+) create mode 100644 drivers/clocksource/mmio.c (limited to 'drivers/clocksource/mmio.c') diff --git a/drivers/clocksource/mmio.c b/drivers/clocksource/mmio.c new file mode 100644 index 000000000..0fee8edb8 --- /dev/null +++ b/drivers/clocksource/mmio.c @@ -0,0 +1,75 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Generic MMIO clocksource support + */ +#include +#include +#include +#include + +struct clocksource_mmio { + void __iomem *reg; + struct clocksource clksrc; +}; + +static inline struct clocksource_mmio *to_mmio_clksrc(struct clocksource *c) +{ + return container_of(c, struct clocksource_mmio, clksrc); +} + +u64 clocksource_mmio_readl_up(struct clocksource *c) +{ + return (u64)readl_relaxed(to_mmio_clksrc(c)->reg); +} +EXPORT_SYMBOL_GPL(clocksource_mmio_readl_up); + +u64 clocksource_mmio_readl_down(struct clocksource *c) +{ + return ~(u64)readl_relaxed(to_mmio_clksrc(c)->reg) & c->mask; +} +EXPORT_SYMBOL_GPL(clocksource_mmio_readl_down); + +u64 clocksource_mmio_readw_up(struct clocksource *c) +{ + return (u64)readw_relaxed(to_mmio_clksrc(c)->reg); +} +EXPORT_SYMBOL_GPL(clocksource_mmio_readw_up); + +u64 clocksource_mmio_readw_down(struct clocksource *c) +{ + return ~(u64)readw_relaxed(to_mmio_clksrc(c)->reg) & c->mask; +} +EXPORT_SYMBOL_GPL(clocksource_mmio_readw_down); + +/** + * clocksource_mmio_init - Initialize a simple mmio based clocksource + * @base: Virtual address of the clock readout register + * @name: Name of the clocksource + * @hz: Frequency of the clocksource in Hz + * @rating: Rating of the clocksource + * @bits: Number of valid bits + * @read: One of clocksource_mmio_read*() above + */ +int clocksource_mmio_init(void __iomem *base, const char *name, + unsigned long hz, int rating, unsigned bits, + u64 (*read)(struct clocksource *)) +{ + struct clocksource_mmio *cs; + + if (bits > 64 || bits < 16) + return -EINVAL; + + cs = kzalloc_obj(struct clocksource_mmio); + if (!cs) + return -ENOMEM; + + cs->reg = base; + cs->clksrc.name = name; + cs->clksrc.rating = rating; + cs->clksrc.read = read; + cs->clksrc.mask = CLOCKSOURCE_MASK(bits); + cs->clksrc.flags = CLOCK_SOURCE_IS_CONTINUOUS; + + return clocksource_register_hz(&cs->clksrc, hz); +} +EXPORT_SYMBOL_GPL(clocksource_mmio_init); -- cgit v1.3.1