6.1-stable review patch. If anyone has any objections, please let me know.
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From: John David Anglin dave.anglin@bell.net
commit 91428ca9320edbab1211851d82429d33b9cd73ef upstream.
Because of the way the _PAGE_READ is handled in the parisc PTE, an access interruption is not generated when the kernel reads from a region where the _PAGE_READ is zero. The current code was written assuming read access faults would also occur in the kernel.
This change adds user access checks to raw_copy_from_user(). The prober_user() define checks whether user code has read access to a virtual address. Note that page faults are not handled in the exception support for the probe instruction. For this reason, we precede the probe by a ldb access check.
Signed-off-by: John David Anglin dave.anglin@bell.net Signed-off-by: Helge Deller deller@gmx.de Cc: stable@vger.kernel.org # v5.12+ Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/parisc/include/asm/special_insns.h | 28 ++++++++++++++++++++++++++++ arch/parisc/lib/memcpy.c | 19 ++++++++++++++++++- 2 files changed, 46 insertions(+), 1 deletion(-)
--- a/arch/parisc/include/asm/special_insns.h +++ b/arch/parisc/include/asm/special_insns.h @@ -32,6 +32,34 @@ pa; \ })
+/** + * prober_user() - Probe user read access + * @sr: Space regster. + * @va: Virtual address. + * + * Return: Non-zero if address is accessible. + * + * Due to the way _PAGE_READ is handled in TLB entries, we need + * a special check to determine whether a user address is accessible. + * The ldb instruction does the initial access check. If it is + * successful, the probe instruction checks user access rights. + */ +#define prober_user(sr, va) ({ \ + unsigned long read_allowed; \ + __asm__ __volatile__( \ + "copy %%r0,%0\n" \ + "8:\tldb 0(%%sr%1,%2),%%r0\n" \ + "\tproberi (%%sr%1,%2),%3,%0\n" \ + "9:\n" \ + ASM_EXCEPTIONTABLE_ENTRY(8b, 9b, \ + "or %%r0,%%r0,%%r0") \ + : "=&r" (read_allowed) \ + : "i" (sr), "r" (va), "i" (PRIV_USER) \ + : "memory" \ + ); \ + read_allowed; \ +}) + #define CR_EIEM 15 /* External Interrupt Enable Mask */ #define CR_CR16 16 /* CR16 Interval Timer */ #define CR_EIRR 23 /* External Interrupt Request Register */ --- a/arch/parisc/lib/memcpy.c +++ b/arch/parisc/lib/memcpy.c @@ -12,6 +12,7 @@ #include <linux/module.h> #include <linux/compiler.h> #include <linux/uaccess.h> +#include <linux/mm.h>
#define get_user_space() mfsp(SR_USER) #define get_kernel_space() SR_KERNEL @@ -32,9 +33,25 @@ EXPORT_SYMBOL(raw_copy_to_user); unsigned long raw_copy_from_user(void *dst, const void __user *src, unsigned long len) { + unsigned long start = (unsigned long) src; + unsigned long end = start + len; + unsigned long newlen = len; + mtsp(get_user_space(), SR_TEMP1); mtsp(get_kernel_space(), SR_TEMP2); - return pa_memcpy(dst, (void __force *)src, len); + + /* Check region is user accessible */ + if (start) + while (start < end) { + if (!prober_user(SR_TEMP1, start)) { + newlen = (start - (unsigned long) src); + break; + } + start += PAGE_SIZE; + /* align to page boundry which may have different permission */ + start = PAGE_ALIGN_DOWN(start); + } + return len - newlen + pa_memcpy(dst, (void __force *)src, newlen); } EXPORT_SYMBOL(raw_copy_from_user);