3.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Kristina Martsenko <kristina.martsenko@xxxxxxx> commit 7dcd9dd8cebe9fa626af7e2358d03a37041a70fb upstream. When we take a watchpoint exception, the address that triggered the watchpoint is found in FAR_EL1. We compare it to the address of each configured watchpoint to see which one was hit. The configured watchpoint addresses are untagged, while the address in FAR_EL1 will have an address tag if the data access was done using a tagged address. The tag needs to be removed to compare the address to the watchpoints. Currently we don't remove it, and as a result can report the wrong watchpoint as being hit (specifically, always either the highest TTBR0 watchpoint or lowest TTBR1 watchpoint). This patch removes the tag. Fixes: d50240a5f6ce ("arm64: mm: permit use of tagged pointers at EL0") Acked-by: Mark Rutland <mark.rutland@xxxxxxx> Acked-by: Will Deacon <will.deacon@xxxxxxx> Signed-off-by: Kristina Martsenko <kristina.martsenko@xxxxxxx> Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/arm64/include/asm/uaccess.h | 8 ++++++++ arch/arm64/kernel/hw_breakpoint.c | 3 ++- include/linux/bitops.h | 11 +++++++++++ 3 files changed, 21 insertions(+), 1 deletion(-) --- a/arch/arm64/include/asm/uaccess.h +++ b/arch/arm64/include/asm/uaccess.h @@ -21,6 +21,7 @@ /* * User space memory access functions */ +#include <linux/bitops.h> #include <linux/string.h> #include <linux/thread_info.h> @@ -100,6 +101,13 @@ static inline void set_fs(mm_segment_t f flag; \ }) +/* + * When dealing with data aborts, watchpoints, or instruction traps we may end + * up with a tagged userland pointer. Clear the tag to get a sane pointer to + * pass on to access_ok(), for instance. + */ +#define untagged_addr(addr) sign_extend64(addr, 55) + #define access_ok(type, addr, size) __range_ok(addr, size) #define user_addr_max get_fs --- a/arch/arm64/kernel/hw_breakpoint.c +++ b/arch/arm64/kernel/hw_breakpoint.c @@ -35,6 +35,7 @@ #include <asm/traps.h> #include <asm/cputype.h> #include <asm/system_misc.h> +#include <asm/uaccess.h> /* Breakpoint currently in use for each BRP. */ static DEFINE_PER_CPU(struct perf_event *, bp_on_reg[ARM_MAX_BRP]); @@ -688,7 +689,7 @@ static int watchpoint_handler(unsigned l /* Check if the watchpoint value matches. */ val = read_wb_reg(AARCH64_DBG_REG_WVR, i); - if (val != (addr & ~alignment_mask)) + if (val != (untagged_addr(addr) & ~alignment_mask)) goto unlock; /* Possible match, check the byte address select to confirm. */ --- a/include/linux/bitops.h +++ b/include/linux/bitops.h @@ -171,6 +171,17 @@ static inline __s32 sign_extend32(__u32 return (__s32)(value << shift) >> shift; } +/** + * sign_extend64 - sign extend a 64-bit value using specified bit as sign-bit + * @value: value to sign extend + * @index: 0 based bit index (0<=index<64) to sign bit + */ +static inline __s64 sign_extend64(__u64 value, int index) +{ + __u8 shift = 63 - index; + return (__s64)(value << shift) >> shift; +} + static inline unsigned fls_long(unsigned long l) { if (sizeof(l) == 4)