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Alexandre Ghiti 258b867f40 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>		History 2023-08-23 17:32:51 +02:00
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clear_page.S	RISC-V: Use Zicboz in clear_page when available	2023-03-14 21:26:06 -07:00
delay.c	include/linux/delay.h: replace kernel.h with the necessary inclusions	2021-11-09 10:02:49 -08:00
error-inject.c	riscv: Add support for function error injection	2021-01-14 15:09:09 -08:00
Makefile	RISC-V: Use Zicboz in clear_page when available	2023-03-14 21:26:06 -07:00
memcpy.S	riscv: Allow to downgrade paging mode from the command line	2023-04-26 07:30:52 -07:00
memmove.S	riscv: Allow to downgrade paging mode from the command line	2023-04-26 07:30:52 -07:00
memset.S	riscv: Add KASAN support	2020-01-22 13:09:58 -08:00
strcmp.S	riscv: lib: Include hwcap.h directly	2023-03-14 20:51:24 -07:00
strlen.S	riscv: Allow to downgrade paging mode from the command line	2023-04-26 07:30:52 -07:00
strncmp.S	riscv: lib: Include hwcap.h directly	2023-03-14 20:51:24 -07:00
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	2023-08-23 17:32:51 +02:00