[PATCH OLK-5.10 08/67] arm64/sve: Better handle failure to allocate SVE register storage

From: Mark Brown broonie@kernel.org

mainline inclusion from mainline-v5.15-rc1 commit 7559b7d7d651d397debbcd838bd49ec4b9e0a4a4 category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I8E73O CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...

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Currently we "handle" failure to allocate the SVE register storage by doing a BUG_ON() and hoping for the best. This is obviously not great and the memory allocation failure will already be loud enough without the BUG_ON(). As the comment says it is a corner case but let's try to do a bit better, remove the BUG_ON() and add code to handle the failure in the callers.

For the ptrace and signal code we can return -ENOMEM gracefully however we have no real error reporting path available to us for the SVE access trap so instead generate a SIGKILL if the allocation fails there. This at least means that we won't try to soldier on and end up trying to access the nonexistant state and while it's obviously not ideal for userspace SIGKILL doesn't allow any handling so minimises the ABI impact, making it easier to improve the interface later if we come up with a better idea.

Signed-off-by: Mark Brown broonie@kernel.org Link: https://lore.kernel.org/r/20210824153417.18371-1-broonie@kernel.org Signed-off-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Wang ShaoBo bobo.shaobowang@huawei.com --- arch/arm64/kernel/fpsimd.c | 10 ++++------ arch/arm64/kernel/ptrace.c | 5 +++++ arch/arm64/kernel/signal.c | 5 +++++ 3 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c index 3599b9a2f1dff..de82f71f63f98 100644 --- a/arch/arm64/kernel/fpsimd.c +++ b/arch/arm64/kernel/fpsimd.c @@ -518,12 +518,6 @@ void sve_alloc(struct task_struct *task) /* This is a small allocation (maximum ~8KB) and Should Not Fail. */ task->thread.sve_state = kzalloc(sve_state_size(task), GFP_KERNEL); - - /* - * If future SVE revisions can have larger vectors though, - * this may cease to be true: - */ - BUG_ON(!task->thread.sve_state); }

@@ -943,6 +937,10 @@ void do_sve_acc(unsigned int esr, struct pt_regs *regs) }

sve_alloc(current); + if (!current->thread.sve_state) { + force_sig(SIGKILL); + return; + }

get_cpu_fpsimd_context();

diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c index 74b925c8d534e..03b84ab27519e 100644 --- a/arch/arm64/kernel/ptrace.c +++ b/arch/arm64/kernel/ptrace.c @@ -846,6 +846,11 @@ static int sve_set(struct task_struct *target, }

sve_alloc(target); + if (!target->thread.sve_state) { + ret = -ENOMEM; + clear_tsk_thread_flag(target, TIF_SVE); + goto out; + }

/* * Ensure target->thread.sve_state is up to date with target's diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c index 17cb54d1e420b..d45d94049e89c 100644 --- a/arch/arm64/kernel/signal.c +++ b/arch/arm64/kernel/signal.c @@ -243,6 +243,11 @@ int restore_sve_fpsimd_context(struct user_ctxs *user) /* From now, fpsimd_thread_switch() won't touch thread.sve_state */

sve_alloc(current); + if (!current->thread.sve_state) { + clear_thread_flag(TIF_SVE); + return -ENOMEM; + } + err = __copy_from_user(current->thread.sve_state, (char __user const *)user->sve + SVE_SIG_REGS_OFFSET,