Alexandre Ghiti e9b8ee715d riscv: uaccess: Return the number of bytes effectively not copied ... [ Upstream commit 4b05b99390 ] It was reported that the riscv kernel hangs while executing the test in [1]. Indeed, the test hangs when trying to write a buffer to a file. The problem is that the riscv implementation of raw_copy_from_user() does not return the correct number of bytes not written when an exception happens and is fixed up, instead it always returns the initial size to copy, even if some bytes were actually copied. generic_perform_write() pre-faults the user pages and bails out if nothing can be written, otherwise it will access the userspace buffer: here the riscv implementation keeps returning it was not able to copy any byte though the pre-faulting indicates otherwise. So generic_perform_write() keeps retrying to access the user memory and ends up in an infinite loop. Note that before the commit mentioned in [1] that introduced this regression, it worked because generic_perform_write() would bail out if only one byte could not be written. So fix this by returning the number of bytes effectively not written in __asm_copy_[to|from]_user() and __clear_user(), as it is expected. Link: https://lore.kernel.org/linux-riscv/20230309151841.bomov6hq3ybyp42a@debian/ [1] Fixes: ebcbd75e39 ("riscv: Fix the bug in memory access fixup code") Reported-by: Bo YU <tsu.yubo@gmail.com> Closes: https://lore.kernel.org/linux-riscv/20230309151841.bomov6hq3ybyp42a@debian/#t Reported-by: Aurelien Jarno <aurelien@aurel32.net> Closes: https://lore.kernel.org/linux-riscv/ZNOnCakhwIeue3yr@aurel32.net/ Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com> Reviewed-by: Björn Töpel <bjorn@rivosinc.com> Tested-by: Aurelien Jarno <aurelien@aurel32.net> Reviewed-by: Aurelien Jarno <aurelien@aurel32.net> Link: https://lore.kernel.org/r/20230811150604.1621784-1-alexghiti@rivosinc.com Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com> Signed-off-by: Sasha Levin <sashal@kernel.org>		2023-08-26 14:23:36 +02:00
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Makefile	riscv: Add support for function error injection	2021-01-14 15:09:09 -08:00
delay.c	riscv: delay: use do_div() instead of __udivdi3()	2019-08-08 16:05:38 -07:00
error-inject.c	riscv: Add support for function error injection	2021-01-14 15:09:09 -08:00
memcpy.S	riscv: Add KASAN support	2020-01-22 13:09:58 -08:00
memmove.S	riscv: Fixed misaligned memory access. Fixed pointer comparison.	2022-04-13 20:59:09 +02:00
memset.S	riscv: Add KASAN support	2020-01-22 13:09:58 -08:00
tishift.S	riscv: Less inefficient gcc tishift helpers (and export their symbols)	2020-01-18 19:13:41 -08:00
uaccess.S	riscv: uaccess: Return the number of bytes effectively not copied	2023-08-26 14:23:36 +02:00