Merge branch 'uprobes/core' of git://git.kernel.org/pub/scm/linux/kernel/git/oleg/misc into perf/urgent

Pull various uprobes bugfixes from Oleg Nesterov - mostly race and
failure path fixes.

Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 162 insertions, 183 deletions

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 98256bc71ee1..5cc4e7e42e68 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -78,15 +78,23 @@ static struct mutex uprobes_mmap_mutex[UPROBES_HASH_SZ];
  */
 static atomic_t uprobe_events = ATOMIC_INIT(0);
 
+/* Have a copy of original instruction */
+#define UPROBE_COPY_INSN        0
+/* Dont run handlers when first register/ last unregister in progress*/
+#define UPROBE_RUN_HANDLER      1
+/* Can skip singlestep */
+#define UPROBE_SKIP_SSTEP       2
+
 struct uprobe {
         struct rb_node          rb_node;        /* node in the rb tree */
         atomic_t                ref;
         struct rw_semaphore     consumer_rwsem;
+        struct mutex            copy_mutex;     /* TODO: kill me and UPROBE_COPY_INSN */
         struct list_head        pending_list;
         struct uprobe_consumer  *consumers;
         struct inode            *inode;         /* Also hold a ref to inode */
         loff_t                  offset;
-        int                     flags;
+        unsigned long           flags;
         struct arch_uprobe      arch;
 };
 
@@ -100,17 +108,12 @@ struct uprobe {
  */
 static bool valid_vma(struct vm_area_struct *vma, bool is_register)
 {
-        if (!vma->vm_file)
-                return false;
-
-        if (!is_register)
-                return true;
+        vm_flags_t flags = VM_HUGETLB | VM_MAYEXEC | VM_SHARED;
 
-        if ((vma->vm_flags & (VM_HUGETLB|VM_READ|VM_WRITE|VM_EXEC|VM_SHARED))
-                                == (VM_READ|VM_EXEC))
-                return true;
+        if (is_register)
+                flags |= VM_WRITE;
 
-        return false;
+        return vma->vm_file && (vma->vm_flags & flags) == VM_MAYEXEC;
 }
 
 static unsigned long offset_to_vaddr(struct vm_area_struct *vma, loff_t offset)
@@ -193,19 +196,44 @@ bool __weak is_swbp_insn(uprobe_opcode_t *insn)
         return *insn == UPROBE_SWBP_INSN;
 }
 
+static void copy_opcode(struct page *page, unsigned long vaddr, uprobe_opcode_t *opcode)
+{
+        void *kaddr = kmap_atomic(page);
+        memcpy(opcode, kaddr + (vaddr & ~PAGE_MASK), UPROBE_SWBP_INSN_SIZE);
+        kunmap_atomic(kaddr);
+}
+
+static int verify_opcode(struct page *page, unsigned long vaddr, uprobe_opcode_t *new_opcode)
+{
+        uprobe_opcode_t old_opcode;
+        bool is_swbp;
+
+        copy_opcode(page, vaddr, &old_opcode);
+        is_swbp = is_swbp_insn(&old_opcode);
+
+        if (is_swbp_insn(new_opcode)) {
+                if (is_swbp)            /* register: already installed? */
+                        return 0;
+        } else {
+                if (!is_swbp)           /* unregister: was it changed by us? */
+                        return 0;
+        }
+
+        return 1;
+}
+
 /*
  * NOTE:
  * Expect the breakpoint instruction to be the smallest size instruction for
  * the architecture. If an arch has variable length instruction and the
  * breakpoint instruction is not of the smallest length instruction
- * supported by that architecture then we need to modify read_opcode /
+ * supported by that architecture then we need to modify is_swbp_at_addr and
  * write_opcode accordingly. This would never be a problem for archs that
  * have fixed length instructions.
  */
 
 /*
  * write_opcode - write the opcode at a given virtual address.
- * @auprobe: arch breakpointing information.
  * @mm: the probed process address space.
  * @vaddr: the virtual address to store the opcode.
  * @opcode: opcode to be written at @vaddr.
@@ -216,8 +244,8 @@ bool __weak is_swbp_insn(uprobe_opcode_t *insn)
  * For mm @mm, write the opcode at @vaddr.
  * Return 0 (success) or a negative errno.
  */
-static int write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm,
-                        unsigned long vaddr, uprobe_opcode_t opcode)
+static int write_opcode(struct mm_struct *mm, unsigned long vaddr,
+                        uprobe_opcode_t opcode)
 {
         struct page *old_page, *new_page;
         void *vaddr_old, *vaddr_new;
@@ -226,10 +254,14 @@ static int write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm,
 
 retry:
         /* Read the page with vaddr into memory */
-        ret = get_user_pages(NULL, mm, vaddr, 1, 0, 0, &old_page, &vma);
+        ret = get_user_pages(NULL, mm, vaddr, 1, 0, 1, &old_page, &vma);
         if (ret <= 0)
                 return ret;
 
+        ret = verify_opcode(old_page, vaddr, &opcode);
+        if (ret <= 0)
+                goto put_old;
+
         ret = -ENOMEM;
         new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vaddr);
         if (!new_page)
@@ -264,63 +296,6 @@ put_old:
 }
 
 /**
- * read_opcode - read the opcode at a given virtual address.
- * @mm: the probed process address space.
- * @vaddr: the virtual address to read the opcode.
- * @opcode: location to store the read opcode.
- *
- * Called with mm->mmap_sem held (for read and with a reference to
- * mm.
- *
- * For mm @mm, read the opcode at @vaddr and store it in @opcode.
- * Return 0 (success) or a negative errno.
- */
-static int read_opcode(struct mm_struct *mm, unsigned long vaddr, uprobe_opcode_t *opcode)
-{
-        struct page *page;
-        void *vaddr_new;
-        int ret;
-
-        ret = get_user_pages(NULL, mm, vaddr, 1, 0, 1, &page, NULL);
-        if (ret <= 0)
-                return ret;
-
-        vaddr_new = kmap_atomic(page);
-        vaddr &= ~PAGE_MASK;
-        memcpy(opcode, vaddr_new + vaddr, UPROBE_SWBP_INSN_SIZE);
-        kunmap_atomic(vaddr_new);
-
-        put_page(page);
-
-        return 0;
-}
-
-static int is_swbp_at_addr(struct mm_struct *mm, unsigned long vaddr)
-{
-        uprobe_opcode_t opcode;
-        int result;
-
-        if (current->mm == mm) {
-                pagefault_disable();
-                result = __copy_from_user_inatomic(&opcode, (void __user*)vaddr,
-                                                                sizeof(opcode));
-                pagefault_enable();
-
-                if (likely(result == 0))
-                        goto out;
-        }
-
-        result = read_opcode(mm, vaddr, &opcode);
-        if (result)
-                return result;
-out:
-        if (is_swbp_insn(&opcode))
-                return 1;
-
-        return 0;
-}
-
-/**
  * set_swbp - store breakpoint at a given address.
  * @auprobe: arch specific probepoint information.
  * @mm: the probed process address space.
@@ -331,18 +306,7 @@ out:
  */
 int __weak set_swbp(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr)
 {
-        int result;
-        /*
-         * See the comment near uprobes_hash().
-         */
-        result = is_swbp_at_addr(mm, vaddr);
-        if (result == 1)
-                return 0;
-
-        if (result)
-                return result;
-
-        return write_opcode(auprobe, mm, vaddr, UPROBE_SWBP_INSN);
+        return write_opcode(mm, vaddr, UPROBE_SWBP_INSN);
 }
 
 /**
@@ -357,16 +321,7 @@ int __weak set_swbp(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned
 int __weak
 set_orig_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr)
 {
-        int result;
-
-        result = is_swbp_at_addr(mm, vaddr);
-        if (!result)
-                return -EINVAL;
-
-        if (result != 1)
-                return result;
-
-        return write_opcode(auprobe, mm, vaddr, *(uprobe_opcode_t *)auprobe->insn);
+        return write_opcode(mm, vaddr, *(uprobe_opcode_t *)auprobe->insn);
 }
 
 static int match_uprobe(struct uprobe *l, struct uprobe *r)
@@ -473,7 +428,7 @@ static struct uprobe *insert_uprobe(struct uprobe *uprobe)
         spin_unlock(&uprobes_treelock);
 
         /* For now assume that the instruction need not be single-stepped */
-        uprobe->flags |= UPROBE_SKIP_SSTEP;
+        __set_bit(UPROBE_SKIP_SSTEP, &uprobe->flags);
 
         return u;
 }
@@ -495,6 +450,7 @@ static struct uprobe *alloc_uprobe(struct inode *inode, loff_t offset)
         uprobe->inode = igrab(inode);
         uprobe->offset = offset;
         init_rwsem(&uprobe->consumer_rwsem);
+        mutex_init(&uprobe->copy_mutex);
 
         /* add to uprobes_tree, sorted on inode:offset */
         cur_uprobe = insert_uprobe(uprobe);
@@ -515,7 +471,7 @@ static void handler_chain(struct uprobe *uprobe, struct pt_regs *regs)
 {
         struct uprobe_consumer *uc;
 
-        if (!(uprobe->flags & UPROBE_RUN_HANDLER))
+        if (!test_bit(UPROBE_RUN_HANDLER, &uprobe->flags))
                 return;
 
         down_read(&uprobe->consumer_rwsem);
@@ -621,29 +577,43 @@ static int copy_insn(struct uprobe *uprobe, struct file *filp)
         return __copy_insn(mapping, filp, uprobe->arch.insn, bytes, uprobe->offset);
 }
 
-/*
- * How mm->uprobes_state.count gets updated
- * uprobe_mmap() increments the count if
- *      - it successfully adds a breakpoint.
- *      - it cannot add a breakpoint, but sees that there is a underlying
- *        breakpoint (via a is_swbp_at_addr()).
- *
- * uprobe_munmap() decrements the count if
- *      - it sees a underlying breakpoint, (via is_swbp_at_addr)
- *        (Subsequent uprobe_unregister wouldnt find the breakpoint
- *        unless a uprobe_mmap kicks in, since the old vma would be
- *        dropped just after uprobe_munmap.)
- *
- * uprobe_register increments the count if:
- *      - it successfully adds a breakpoint.
- *
- * uprobe_unregister decrements the count if:
- *      - it sees a underlying breakpoint and removes successfully.
- *        (via is_swbp_at_addr)
- *        (Subsequent uprobe_munmap wouldnt find the breakpoint
- *        since there is no underlying breakpoint after the
- *        breakpoint removal.)
- */
+static int prepare_uprobe(struct uprobe *uprobe, struct file *file,
+                                struct mm_struct *mm, unsigned long vaddr)
+{
+        int ret = 0;
+
+        if (test_bit(UPROBE_COPY_INSN, &uprobe->flags))
+                return ret;
+
+        mutex_lock(&uprobe->copy_mutex);
+        if (test_bit(UPROBE_COPY_INSN, &uprobe->flags))
+                goto out;
+
+        ret = copy_insn(uprobe, file);
+        if (ret)
+                goto out;
+
+        ret = -ENOTSUPP;
+        if (is_swbp_insn((uprobe_opcode_t *)uprobe->arch.insn))
+                goto out;
+
+        ret = arch_uprobe_analyze_insn(&uprobe->arch, mm, vaddr);
+        if (ret)
+                goto out;
+
+        /* write_opcode() assumes we don't cross page boundary */
+        BUG_ON((uprobe->offset & ~PAGE_MASK) +
+                        UPROBE_SWBP_INSN_SIZE > PAGE_SIZE);
+
+        smp_wmb(); /* pairs with rmb() in find_active_uprobe() */
+        set_bit(UPROBE_COPY_INSN, &uprobe->flags);
+
+ out:
+        mutex_unlock(&uprobe->copy_mutex);
+
+        return ret;
+}
+
 static int
 install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm,
                         struct vm_area_struct *vma, unsigned long vaddr)
@@ -661,24 +631,9 @@ install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm,
         if (!uprobe->consumers)
                 return 0;
 
-        if (!(uprobe->flags & UPROBE_COPY_INSN)) {
-                ret = copy_insn(uprobe, vma->vm_file);
-                if (ret)
-                        return ret;
-
-                if (is_swbp_insn((uprobe_opcode_t *)uprobe->arch.insn))
-                        return -ENOTSUPP;
-
-                ret = arch_uprobe_analyze_insn(&uprobe->arch, mm, vaddr);
-                if (ret)
-                        return ret;
-
-                /* write_opcode() assumes we don't cross page boundary */
-                BUG_ON((uprobe->offset & ~PAGE_MASK) +
-                                UPROBE_SWBP_INSN_SIZE > PAGE_SIZE);
-
-                uprobe->flags |= UPROBE_COPY_INSN;
-        }
+        ret = prepare_uprobe(uprobe, vma->vm_file, mm, vaddr);
+        if (ret)
+                return ret;
 
         /*
          * set MMF_HAS_UPROBES in advance for uprobe_pre_sstep_notifier(),
@@ -697,15 +652,15 @@ install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm,
         return ret;
 }
 
-static void
+static int
 remove_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, unsigned long vaddr)
 {
         /* can happen if uprobe_register() fails */
         if (!test_bit(MMF_HAS_UPROBES, &mm->flags))
-                return;
+                return 0;
 
         set_bit(MMF_RECALC_UPROBES, &mm->flags);
-        set_orig_insn(&uprobe->arch, mm, vaddr);
+        return set_orig_insn(&uprobe->arch, mm, vaddr);
 }
 
 /*
@@ -820,7 +775,7 @@ static int register_for_each_vma(struct uprobe *uprobe, bool is_register)
                 struct mm_struct *mm = info->mm;
                 struct vm_area_struct *vma;
 
-                if (err)
+                if (err && is_register)
                         goto free;
 
                 down_write(&mm->mmap_sem);
@@ -836,7 +791,7 @@ static int register_for_each_vma(struct uprobe *uprobe, bool is_register)
                 if (is_register)
                         err = install_breakpoint(uprobe, mm, vma, info->vaddr);
                 else
-                        remove_breakpoint(uprobe, mm, info->vaddr);
+                        err |= remove_breakpoint(uprobe, mm, info->vaddr);
 
  unlock:
                 up_write(&mm->mmap_sem);
@@ -893,13 +848,15 @@ int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer *
         mutex_lock(uprobes_hash(inode));
         uprobe = alloc_uprobe(inode, offset);
 
-        if (uprobe && !consumer_add(uprobe, uc)) {
+        if (!uprobe) {
+                ret = -ENOMEM;
+        } else if (!consumer_add(uprobe, uc)) {
                 ret = __uprobe_register(uprobe);
                 if (ret) {
                         uprobe->consumers = NULL;
                         __uprobe_unregister(uprobe);
                 } else {
-                        uprobe->flags |= UPROBE_RUN_HANDLER;
+                        set_bit(UPROBE_RUN_HANDLER, &uprobe->flags);
                 }
         }
 
@@ -932,7 +889,7 @@ void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consume
         if (consumer_del(uprobe, uc)) {
                 if (!uprobe->consumers) {
                         __uprobe_unregister(uprobe);
-                        uprobe->flags &= ~UPROBE_RUN_HANDLER;
+                        clear_bit(UPROBE_RUN_HANDLER, &uprobe->flags);
                 }
         }
 
@@ -1393,10 +1350,11 @@ bool uprobe_deny_signal(void)
  */
 static bool can_skip_sstep(struct uprobe *uprobe, struct pt_regs *regs)
 {
-        if (arch_uprobe_skip_sstep(&uprobe->arch, regs))
-                return true;
-
-        uprobe->flags &= ~UPROBE_SKIP_SSTEP;
+        if (test_bit(UPROBE_SKIP_SSTEP, &uprobe->flags)) {
+                if (arch_uprobe_skip_sstep(&uprobe->arch, regs))
+                        return true;
+                clear_bit(UPROBE_SKIP_SSTEP, &uprobe->flags);
+        }
         return false;
 }
 
@@ -1419,6 +1377,30 @@ static void mmf_recalc_uprobes(struct mm_struct *mm)
         clear_bit(MMF_HAS_UPROBES, &mm->flags);
 }
 
+static int is_swbp_at_addr(struct mm_struct *mm, unsigned long vaddr)
+{
+        struct page *page;
+        uprobe_opcode_t opcode;
+        int result;
+
+        pagefault_disable();
+        result = __copy_from_user_inatomic(&opcode, (void __user*)vaddr,
+                                                        sizeof(opcode));
+        pagefault_enable();
+
+        if (likely(result == 0))
+                goto out;
+
+        result = get_user_pages(NULL, mm, vaddr, 1, 0, 1, &page, NULL);
+        if (result < 0)
+                return result;
+
+        copy_opcode(page, vaddr, &opcode);
+        put_page(page);
+ out:
+        return is_swbp_insn(&opcode);
+}
+
 static struct uprobe *find_active_uprobe(unsigned long bp_vaddr, int *is_swbp)
 {
         struct mm_struct *mm = current->mm;
@@ -1489,38 +1471,41 @@ static void handle_swbp(struct pt_regs *regs)
                 }
                 return;
         }
+        /*
+         * TODO: move copy_insn/etc into _register and remove this hack.
+         * After we hit the bp, _unregister + _register can install the
+         * new and not-yet-analyzed uprobe at the same address, restart.
+         */
+        smp_rmb(); /* pairs with wmb() in install_breakpoint() */
+        if (unlikely(!test_bit(UPROBE_COPY_INSN, &uprobe->flags)))
+                goto restart;
 
         utask = current->utask;
         if (!utask) {
                 utask = add_utask();
                 /* Cannot allocate; re-execute the instruction. */
                 if (!utask)
-                        goto cleanup_ret;
+                        goto restart;
         }
-        utask->active_uprobe = uprobe;
+
         handler_chain(uprobe, regs);
-        if (uprobe->flags & UPROBE_SKIP_SSTEP && can_skip_sstep(uprobe, regs))
-                goto cleanup_ret;
+        if (can_skip_sstep(uprobe, regs))
+                goto out;
 
-        utask->state = UTASK_SSTEP;
         if (!pre_ssout(uprobe, regs, bp_vaddr)) {
                 arch_uprobe_enable_step(&uprobe->arch);
+                utask->active_uprobe = uprobe;
+                utask->state = UTASK_SSTEP;
                 return;
         }
 
-cleanup_ret:
-        if (utask) {
-                utask->active_uprobe = NULL;
-                utask->state = UTASK_RUNNING;
-        }
-        if (!(uprobe->flags & UPROBE_SKIP_SSTEP))
-
-                /*
-                 * cannot singlestep; cannot skip instruction;
-                 * re-execute the instruction.
-                 */
-                instruction_pointer_set(regs, bp_vaddr);
-
+restart:
+        /*
+         * cannot singlestep; cannot skip instruction;
+         * re-execute the instruction.
+         */
+        instruction_pointer_set(regs, bp_vaddr);
+out:
         put_uprobe(uprobe);
 }
 
@@ -1552,13 +1537,12 @@ static void handle_singlestep(struct uprobe_task *utask, struct pt_regs *regs)
 }
 
 /*
- * On breakpoint hit, breakpoint notifier sets the TIF_UPROBE flag.  (and on
- * subsequent probe hits on the thread sets the state to UTASK_BP_HIT) and
- * allows the thread to return from interrupt.
+ * On breakpoint hit, breakpoint notifier sets the TIF_UPROBE flag and
+ * allows the thread to return from interrupt. After that handle_swbp()
+ * sets utask->active_uprobe.
  *
- * On singlestep exception, singlestep notifier sets the TIF_UPROBE flag and
- * also sets the state to UTASK_SSTEP_ACK and allows the thread to return from
- * interrupt.
+ * On singlestep exception, singlestep notifier sets the TIF_UPROBE flag
+ * and allows the thread to return from interrupt.
  *
  * While returning to userspace, thread notices the TIF_UPROBE flag and calls
  * uprobe_notify_resume().
@@ -1567,11 +1551,13 @@ void uprobe_notify_resume(struct pt_regs *regs)
 {
         struct uprobe_task *utask;
 
+        clear_thread_flag(TIF_UPROBE);
+
         utask = current->utask;
-        if (!utask || utask->state == UTASK_BP_HIT)
-                handle_swbp(regs);
-        else
+        if (utask && utask->active_uprobe)
                 handle_singlestep(utask, regs);
+        else
+                handle_swbp(regs);
 }
 
 /*
@@ -1580,17 +1566,10 @@ void uprobe_notify_resume(struct pt_regs *regs)
  */
 int uprobe_pre_sstep_notifier(struct pt_regs *regs)
 {
-        struct uprobe_task *utask;
-
         if (!current->mm || !test_bit(MMF_HAS_UPROBES, &current->mm->flags))
                 return 0;
 
-        utask = current->utask;
-        if (utask)
-                utask->state = UTASK_BP_HIT;
-
         set_thread_flag(TIF_UPROBE);
-
         return 1;
 }