kernel/linux.git/arch/parisc/include/asm/uaccess.h, branch linux-7.1.y

parisc: Revise __get_user() to probe user read access

2025-07-25T20:45:24+00:00

Because of the way read access support is implemented, read access interruptions are only triggered at privilege levels 2 and 3. The kernel executes at privilege level 0, so __get_user() never triggers a read access interruption (code 26). Thus, it is currently possible for user code to access a read protected address via a system call. Fix this by probing read access rights at privilege level 3 (PRIV_USER) and setting __gu_err to -EFAULT (-14) if access isn't allowed. Note the cmpiclr instruction does a 32-bit compare because COND macro doesn't work inside asm. Signed-off-by: John David Anglin Signed-off-by: Helge Deller Cc: stable@vger.kernel.org # v5.12+

parisc: Fix random data corruption from exception handler

2024-01-30T16:18:58+00:00

The current exception handler implementation, which assists when accessing user space memory, may exhibit random data corruption if the compiler decides to use a different register than the specified register %r29 (defined in ASM_EXCEPTIONTABLE_REG) for the error code. If the compiler choose another register, the fault handler will nevertheless store -EFAULT into %r29 and thus trash whatever this register is used for. Looking at the assembly I found that this happens sometimes in emulate_ldd(). To solve the issue, the easiest solution would be if it somehow is possible to tell the fault handler which register is used to hold the error code. Using %0 or %1 in the inline assembly is not posssible as it will show up as e.g. %r29 (with the "%r" prefix), which the GNU assembler can not convert to an integer. This patch takes another, better and more flexible approach: We extend the __ex_table (which is out of the execution path) by one 32-word. In this word we tell the compiler to insert the assembler instruction "or %r0,%r0,%reg", where %reg references the register which the compiler choosed for the error return code. In case of an access failure, the fault handler finds the __ex_table entry and can examine the opcode. The used register is encoded in the lowest 5 bits, and the fault handler can then store -EFAULT into this register. Since we extend the __ex_table to 3 words we can't use the BUILDTIME_TABLE_SORT config option any longer. Signed-off-by: Helge Deller Cc: # v6.0+

parisc: Mark ex_table entries 32-bit aligned in uaccess.h

2023-11-25T08:43:17+00:00

Add an align statement to tell the linker that all ex_table entries and as such the whole ex_table section should be 32-bit aligned in vmlinux and modules. Signed-off-by: Helge Deller Cc: stable@vger.kernel.org # v6.0+

Merge tag 'asm-generic-5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic

2022-03-24T01:03:08+00:00

Pull asm-generic updates from Arnd Bergmann: "There are three sets of updates for 5.18 in the asm-generic tree: - The set_fs()/get_fs() infrastructure gets removed for good. This was already gone from all major architectures, but now we can finally remove it everywhere, which loses some particularly tricky and error-prone code. There is a small merge conflict against a parisc cleanup, the solution is to use their new version. - The nds32 architecture ends its tenure in the Linux kernel. The hardware is still used and the code is in reasonable shape, but the mainline port is not actively maintained any more, as all remaining users are thought to run vendor kernels that would never be updated to a future release. - A series from Masahiro Yamada cleans up some of the uapi header files to pass the compile-time checks" * tag 'asm-generic-5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic: (27 commits) nds32: Remove the architecture uaccess: remove CONFIG_SET_FS ia64: remove CONFIG_SET_FS support sh: remove CONFIG_SET_FS support sparc64: remove CONFIG_SET_FS support lib/test_lockup: fix kernel pointer check for separate address spaces uaccess: generalize access_ok() uaccess: fix type mismatch warnings from access_ok() arm64: simplify access_ok() m68k: fix access_ok for coldfire MIPS: use simpler access_ok() MIPS: Handle address errors for accesses above CPU max virtual user address uaccess: add generic __{get,put}_kernel_nofault nios2: drop access_ok() check from __put_user() x86: use more conventional access_ok() definition x86: remove __range_not_ok() sparc64: add __{get,put}_kernel_nofault() nds32: fix access_ok() checks in get/put_user uaccess: fix nios2 and microblaze get_user_8() sparc64: fix building assembly files ...

parisc: Use SR_USER and SR_KERNEL in get_user() and put_user()

2022-03-11T18:49:30+00:00

Instead of hardcoding the space registers as strings, use the SR_USER and SR_KERNEL constants to form the space register in the access functions. Signed-off-by: Helge Deller

uaccess: generalize access_ok()

2022-02-25T08:36:05+00:00

There are many different ways that access_ok() is defined across architectures, but in the end, they all just compare against the user_addr_max() value or they accept anything. Provide one definition that works for most architectures, checking against TASK_SIZE_MAX for user processes or skipping the check inside of uaccess_kernel() sections. For architectures without CONFIG_SET_FS(), this should be the fastest check, as it comes down to a single comparison of a pointer against a compile-time constant, while the architecture specific versions tend to do something more complex for historic reasons or get something wrong. Type checking for __user annotations is handled inconsistently across architectures, but this is easily simplified as well by using an inline function that takes a 'const void __user *' argument. A handful of callers need an extra __user annotation for this. Some architectures had trick to use 33-bit or 65-bit arithmetic on the addresses to calculate the overflow, however this simpler version uses fewer registers, which means it can produce better object code in the end despite needing a second (statically predicted) branch. Reviewed-by: Christoph Hellwig Acked-by: Mark Rutland [arm64, asm-generic] Acked-by: Geert Uytterhoeven Acked-by: Stafford Horne Acked-by: Dinh Nguyen Signed-off-by: Arnd Bergmann

uaccess: add generic __{get,put}_kernel_nofault

2022-02-25T08:36:05+00:00

Nine architectures are still missing __{get,put}_kernel_nofault: alpha, ia64, microblaze, nds32, nios2, openrisc, sh, sparc32, xtensa. Add a generic version that lets everything use the normal copy_{from,to}_kernel_nofault() code based on these, removing the last use of get_fs()/set_fs() from architecture-independent code. Reviewed-by: Christoph Hellwig Acked-by: Geert Uytterhoeven Signed-off-by: Arnd Bergmann

parisc: Fix some apparent put_user() failures

2022-02-14T11:36:42+00:00

After commit 4b9d2a731c3d ("parisc: Switch user access functions to signal errors in r29 instead of r8") bash suddenly started to report those warnings after login: -bash: cannot set terminal process group (-1): Bad file descriptor -bash: no job control in this shell It turned out, that a function call inside a put_user(), e.g.: put_user(vt_do_kdgkbmode(console), (int __user *)arg); clobbered the error register (r29) and thus the put_user() call itself seem to have failed. Rearrange the C-code to pre-calculate the intermediate value and then do the put_user(). Additionally prefer the "+" constraint on pu_err and gu_err registers to tell the compiler that those operands are both read and written by the assembly instruction. Reported-by: John David Anglin Signed-off-by: Helge Deller Fixes: 4b9d2a731c3d ("parisc: Switch user access functions to signal errors in r29 instead of r8") Signed-off-by: Helge Deller

parisc: Switch user access functions to signal errors in r29 instead of r8

2022-01-07T00:29:21+00:00

Use register r29 instead of register r8 to signal faults when accessing user memory. In case of faults, the fixup routine will store -EFAULT in this register. This change saves up to 752 bytes on a 32bit kernel, partly because the compiler doesn't need to save and restore the old r8 value on the stack. bloat-o-meter results for usage with r29 register: add/remove: 0/0 grow/shrink: 23/86 up/down: 228/-980 (-752) bloat-o-meter results for usage with r28 register: add/remove: 0/0 grow/shrink: 28/83 up/down: 296/-956 (-660) Signed-off-by: Helge Deller

parisc: Implement __get/put_kernel_nofault()

2021-09-09T20:53:09+00:00

Remove CONFIG_SET_FS from parisc, so we need to add __get_kernel_nofault() and __put_kernel_nofault(), define HAVE_GET_KERNEL_NOFAULT and remove set_fs(), get_fs(), load_sr2(), thread_info->addr_limit, KERNEL_DS and USER_DS. The nice side-effect of this patch is that we now can directly access userspace via sr3 without the need to use a temporary sr2 which is either copied from sr3 or set to zero (for kernel space). Signed-off-by: Helge Deller Suggested-by: Arnd Bergmann