6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Alexandre Ghiti alexghiti@rivosinc.com
[ Upstream commit a370c2419e4680a27382d9231edcf739d5d74efc ]
patch_map() uses fixmap mappings to circumvent the non-writability of the kernel text mapping.
The __set_fixmap() function only flushes the current cpu tlb, it does not emit an IPI so we must make sure that while we use a fixmap mapping, the current task is not migrated on another cpu which could miss the newly introduced fixmap mapping.
So in order to avoid any task migration, disable the preemption.
Reported-by: Andrea Parri andrea@rivosinc.com Closes: https://lore.kernel.org/all/ZcS+GAaM25LXsBOl@andrea/ Reported-by: Andy Chiu andy.chiu@sifive.com Closes: https://lore.kernel.org/linux-riscv/CABgGipUMz3Sffu-CkmeUB1dKVwVQ73+7=sgC45-... Fixes: cad539baa48f ("riscv: implement a memset like function for text") Fixes: 0ff7c3b33127 ("riscv: Use text_mutex instead of patch_lock") Co-developed-by: Andy Chiu andy.chiu@sifive.com Signed-off-by: Andy Chiu andy.chiu@sifive.com Signed-off-by: Alexandre Ghiti alexghiti@rivosinc.com Acked-by: Puranjay Mohan puranjay12@gmail.com Link: https://lore.kernel.org/r/20240326203017.310422-3-alexghiti@rivosinc.com Signed-off-by: Palmer Dabbelt palmer@rivosinc.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/riscv/kernel/patch.c | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c index 37e87fdcf6a00..30e12b310cab7 100644 --- a/arch/riscv/kernel/patch.c +++ b/arch/riscv/kernel/patch.c @@ -80,6 +80,8 @@ static int __patch_insn_set(void *addr, u8 c, size_t len) */ lockdep_assert_held(&text_mutex);
+ preempt_disable(); + if (across_pages) patch_map(addr + PAGE_SIZE, FIX_TEXT_POKE1);
@@ -92,6 +94,8 @@ static int __patch_insn_set(void *addr, u8 c, size_t len) if (across_pages) patch_unmap(FIX_TEXT_POKE1);
+ preempt_enable(); + return 0; } NOKPROBE_SYMBOL(__patch_insn_set); @@ -122,6 +126,8 @@ static int __patch_insn_write(void *addr, const void *insn, size_t len) if (!riscv_patch_in_stop_machine) lockdep_assert_held(&text_mutex);
+ preempt_disable(); + if (across_pages) patch_map(addr + PAGE_SIZE, FIX_TEXT_POKE1);
@@ -134,6 +140,8 @@ static int __patch_insn_write(void *addr, const void *insn, size_t len) if (across_pages) patch_unmap(FIX_TEXT_POKE1);
+ preempt_enable(); + return ret; } NOKPROBE_SYMBOL(__patch_insn_write);