Extend /proc/pid/maps tearing tests to verify PROCMAP_QUERY ioctl operation correctness while the vma is being concurrently modified. Signed-off-by: Suren Baghdasaryan Tested-by: SeongJae Park Acked-by: SeongJae Park --- tools/testing/selftests/proc/proc-maps-race.c | 65 +++++++++++++++++++ 1 file changed, 65 insertions(+) diff --git a/tools/testing/selftests/proc/proc-maps-race.c b/tools/testing/selftests/proc/proc-maps-race.c index 94bba4553130..a546475db550 100644 --- a/tools/testing/selftests/proc/proc-maps-race.c +++ b/tools/testing/selftests/proc/proc-maps-race.c @@ -32,6 +32,8 @@ #include #include #include +#include +#include #include #include #include @@ -317,6 +319,25 @@ static bool capture_mod_pattern(FIXTURE_DATA(proc_maps_race) *self, strcmp(restored_first_line->text, self->first_line.text) == 0; } +static bool query_addr_at(int maps_fd, void *addr, + unsigned long *vma_start, unsigned long *vma_end) +{ + struct procmap_query q; + + memset(&q, 0, sizeof(q)); + q.size = sizeof(q); + /* Find the VMA at the split address */ + q.query_addr = (unsigned long long)addr; + q.query_flags = 0; + if (ioctl(maps_fd, PROCMAP_QUERY, &q)) + return false; + + *vma_start = q.vma_start; + *vma_end = q.vma_end; + + return true; +} + static inline bool split_vma(FIXTURE_DATA(proc_maps_race) *self) { return mmap(self->mod_info->addr, self->page_size, self->mod_info->prot | PROT_EXEC, @@ -559,6 +580,8 @@ TEST_F(proc_maps_race, test_maps_tearing_from_split) do { bool last_line_changed; bool first_line_changed; + unsigned long vma_start; + unsigned long vma_end; ASSERT_TRUE(read_boundary_lines(self, &new_last_line, &new_first_line)); @@ -595,6 +618,19 @@ TEST_F(proc_maps_race, test_maps_tearing_from_split) first_line_changed = strcmp(new_first_line.text, self->first_line.text) != 0; ASSERT_EQ(last_line_changed, first_line_changed); + /* Check if PROCMAP_QUERY ioclt() finds the right VMA */ + ASSERT_TRUE(query_addr_at(self->maps_fd, mod_info->addr + self->page_size, + &vma_start, &vma_end)); + /* + * The vma at the split address can be either the same as + * original one (if read before the split) or the same as the + * first line in the second page (if read after the split). + */ + ASSERT_TRUE((vma_start == self->last_line.start_addr && + vma_end == self->last_line.end_addr) || + (vma_start == split_first_line.start_addr && + vma_end == split_first_line.end_addr)); + clock_gettime(CLOCK_MONOTONIC_COARSE, &end_ts); end_test_iteration(&end_ts, self->verbose); } while (end_ts.tv_sec - start_ts.tv_sec < self->duration_sec); @@ -636,6 +672,9 @@ TEST_F(proc_maps_race, test_maps_tearing_from_resize) clock_gettime(CLOCK_MONOTONIC_COARSE, &start_ts); start_test_loop(&start_ts, self->verbose); do { + unsigned long vma_start; + unsigned long vma_end; + ASSERT_TRUE(read_boundary_lines(self, &new_last_line, &new_first_line)); /* Check if we read vmas after shrinking it */ @@ -662,6 +701,16 @@ TEST_F(proc_maps_race, test_maps_tearing_from_resize) "Expand result invalid", self)); } + /* Check if PROCMAP_QUERY ioclt() finds the right VMA */ + ASSERT_TRUE(query_addr_at(self->maps_fd, mod_info->addr, &vma_start, &vma_end)); + /* + * The vma should stay at the same address and have either the + * original size of 3 pages or 1 page if read after shrinking. + */ + ASSERT_TRUE(vma_start == self->last_line.start_addr && + (vma_end - vma_start == self->page_size * 3 || + vma_end - vma_start == self->page_size)); + clock_gettime(CLOCK_MONOTONIC_COARSE, &end_ts); end_test_iteration(&end_ts, self->verbose); } while (end_ts.tv_sec - start_ts.tv_sec < self->duration_sec); @@ -703,6 +752,9 @@ TEST_F(proc_maps_race, test_maps_tearing_from_remap) clock_gettime(CLOCK_MONOTONIC_COARSE, &start_ts); start_test_loop(&start_ts, self->verbose); do { + unsigned long vma_start; + unsigned long vma_end; + ASSERT_TRUE(read_boundary_lines(self, &new_last_line, &new_first_line)); /* Check if we read vmas after remapping it */ @@ -729,6 +781,19 @@ TEST_F(proc_maps_race, test_maps_tearing_from_remap) "Remap restore result invalid", self)); } + /* Check if PROCMAP_QUERY ioclt() finds the right VMA */ + ASSERT_TRUE(query_addr_at(self->maps_fd, mod_info->addr + self->page_size, + &vma_start, &vma_end)); + /* + * The vma should either stay at the same address and have the + * original size of 3 pages or we should find the remapped vma + * at the remap destination address with size of 1 page. + */ + ASSERT_TRUE((vma_start == self->last_line.start_addr && + vma_end - vma_start == self->page_size * 3) || + (vma_start == self->last_line.start_addr + self->page_size && + vma_end - vma_start == self->page_size)); + clock_gettime(CLOCK_MONOTONIC_COARSE, &end_ts); end_test_iteration(&end_ts, self->verbose); } while (end_ts.tv_sec - start_ts.tv_sec < self->duration_sec); -- 2.50.1.703.g449372360f-goog Refactor struct proc_maps_private so that the fields used by PROCMAP_QUERY ioctl are moved into a separate structure. In the next patch this allows ioctl to reuse some of the functions used for reading /proc/pid/maps without using file->private_data. This prevents concurrent modification of file->private_data members by ioctl and /proc/pid/maps readers. The change is pure code refactoring and has no functional changes. Signed-off-by: Suren Baghdasaryan Reviewed-by: Vlastimil Babka Acked-by: SeongJae Park --- fs/proc/internal.h | 15 +++++--- fs/proc/task_mmu.c | 87 +++++++++++++++++++++++--------------------- fs/proc/task_nommu.c | 14 +++---- 3 files changed, 63 insertions(+), 53 deletions(-) diff --git a/fs/proc/internal.h b/fs/proc/internal.h index e737401d7383..d1598576506c 100644 --- a/fs/proc/internal.h +++ b/fs/proc/internal.h @@ -378,16 +378,21 @@ extern void proc_self_init(void); * task_[no]mmu.c */ struct mem_size_stats; -struct proc_maps_private { - struct inode *inode; - struct task_struct *task; + +struct proc_maps_locking_ctx { struct mm_struct *mm; - struct vma_iterator iter; - loff_t last_pos; #ifdef CONFIG_PER_VMA_LOCK bool mmap_locked; struct vm_area_struct *locked_vma; #endif +}; + +struct proc_maps_private { + struct inode *inode; + struct task_struct *task; + struct vma_iterator iter; + loff_t last_pos; + struct proc_maps_locking_ctx lock_ctx; #ifdef CONFIG_NUMA struct mempolicy *task_mempolicy; #endif diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 29cca0e6d0ff..c0968d293b61 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -132,18 +132,18 @@ static void release_task_mempolicy(struct proc_maps_private *priv) #ifdef CONFIG_PER_VMA_LOCK -static void unlock_vma(struct proc_maps_private *priv) +static void unlock_ctx_vma(struct proc_maps_locking_ctx *lock_ctx) { - if (priv->locked_vma) { - vma_end_read(priv->locked_vma); - priv->locked_vma = NULL; + if (lock_ctx->locked_vma) { + vma_end_read(lock_ctx->locked_vma); + lock_ctx->locked_vma = NULL; } } static const struct seq_operations proc_pid_maps_op; static inline bool lock_vma_range(struct seq_file *m, - struct proc_maps_private *priv) + struct proc_maps_locking_ctx *lock_ctx) { /* * smaps and numa_maps perform page table walk, therefore require @@ -151,25 +151,25 @@ static inline bool lock_vma_range(struct seq_file *m, * walking the vma tree under rcu read protection. */ if (m->op != &proc_pid_maps_op) { - if (mmap_read_lock_killable(priv->mm)) + if (mmap_read_lock_killable(lock_ctx->mm)) return false; - priv->mmap_locked = true; + lock_ctx->mmap_locked = true; } else { rcu_read_lock(); - priv->locked_vma = NULL; - priv->mmap_locked = false; + lock_ctx->locked_vma = NULL; + lock_ctx->mmap_locked = false; } return true; } -static inline void unlock_vma_range(struct proc_maps_private *priv) +static inline void unlock_vma_range(struct proc_maps_locking_ctx *lock_ctx) { - if (priv->mmap_locked) { - mmap_read_unlock(priv->mm); + if (lock_ctx->mmap_locked) { + mmap_read_unlock(lock_ctx->mm); } else { - unlock_vma(priv); + unlock_ctx_vma(lock_ctx); rcu_read_unlock(); } } @@ -177,15 +177,16 @@ static inline void unlock_vma_range(struct proc_maps_private *priv) static struct vm_area_struct *get_next_vma(struct proc_maps_private *priv, loff_t last_pos) { + struct proc_maps_locking_ctx *lock_ctx = &priv->lock_ctx; struct vm_area_struct *vma; - if (priv->mmap_locked) + if (lock_ctx->mmap_locked) return vma_next(&priv->iter); - unlock_vma(priv); - vma = lock_next_vma(priv->mm, &priv->iter, last_pos); + unlock_ctx_vma(lock_ctx); + vma = lock_next_vma(lock_ctx->mm, &priv->iter, last_pos); if (!IS_ERR_OR_NULL(vma)) - priv->locked_vma = vma; + lock_ctx->locked_vma = vma; return vma; } @@ -193,14 +194,16 @@ static struct vm_area_struct *get_next_vma(struct proc_maps_private *priv, static inline bool fallback_to_mmap_lock(struct proc_maps_private *priv, loff_t pos) { - if (priv->mmap_locked) + struct proc_maps_locking_ctx *lock_ctx = &priv->lock_ctx; + + if (lock_ctx->mmap_locked) return false; rcu_read_unlock(); - mmap_read_lock(priv->mm); + mmap_read_lock(lock_ctx->mm); /* Reinitialize the iterator after taking mmap_lock */ vma_iter_set(&priv->iter, pos); - priv->mmap_locked = true; + lock_ctx->mmap_locked = true; return true; } @@ -208,14 +211,14 @@ static inline bool fallback_to_mmap_lock(struct proc_maps_private *priv, #else /* CONFIG_PER_VMA_LOCK */ static inline bool lock_vma_range(struct seq_file *m, - struct proc_maps_private *priv) + struct proc_maps_locking_ctx *lock_ctx) { - return mmap_read_lock_killable(priv->mm) == 0; + return mmap_read_lock_killable(lock_ctx->mm) == 0; } -static inline void unlock_vma_range(struct proc_maps_private *priv) +static inline void unlock_vma_range(struct proc_maps_locking_ctx *lock_ctx) { - mmap_read_unlock(priv->mm); + mmap_read_unlock(lock_ctx->mm); } static struct vm_area_struct *get_next_vma(struct proc_maps_private *priv, @@ -258,7 +261,7 @@ static struct vm_area_struct *proc_get_vma(struct seq_file *m, loff_t *ppos) *ppos = vma->vm_end; } else { *ppos = SENTINEL_VMA_GATE; - vma = get_gate_vma(priv->mm); + vma = get_gate_vma(priv->lock_ctx.mm); } return vma; @@ -267,6 +270,7 @@ static struct vm_area_struct *proc_get_vma(struct seq_file *m, loff_t *ppos) static void *m_start(struct seq_file *m, loff_t *ppos) { struct proc_maps_private *priv = m->private; + struct proc_maps_locking_ctx *lock_ctx; loff_t last_addr = *ppos; struct mm_struct *mm; @@ -278,14 +282,15 @@ static void *m_start(struct seq_file *m, loff_t *ppos) if (!priv->task) return ERR_PTR(-ESRCH); - mm = priv->mm; + lock_ctx = &priv->lock_ctx; + mm = lock_ctx->mm; if (!mm || !mmget_not_zero(mm)) { put_task_struct(priv->task); priv->task = NULL; return NULL; } - if (!lock_vma_range(m, priv)) { + if (!lock_vma_range(m, lock_ctx)) { mmput(mm); put_task_struct(priv->task); priv->task = NULL; @@ -318,13 +323,13 @@ static void *m_next(struct seq_file *m, void *v, loff_t *ppos) static void m_stop(struct seq_file *m, void *v) { struct proc_maps_private *priv = m->private; - struct mm_struct *mm = priv->mm; + struct mm_struct *mm = priv->lock_ctx.mm; if (!priv->task) return; release_task_mempolicy(priv); - unlock_vma_range(priv); + unlock_vma_range(&priv->lock_ctx); mmput(mm); put_task_struct(priv->task); priv->task = NULL; @@ -339,9 +344,9 @@ static int proc_maps_open(struct inode *inode, struct file *file, return -ENOMEM; priv->inode = inode; - priv->mm = proc_mem_open(inode, PTRACE_MODE_READ); - if (IS_ERR(priv->mm)) { - int err = PTR_ERR(priv->mm); + priv->lock_ctx.mm = proc_mem_open(inode, PTRACE_MODE_READ); + if (IS_ERR(priv->lock_ctx.mm)) { + int err = PTR_ERR(priv->lock_ctx.mm); seq_release_private(inode, file); return err; @@ -355,8 +360,8 @@ static int proc_map_release(struct inode *inode, struct file *file) struct seq_file *seq = file->private_data; struct proc_maps_private *priv = seq->private; - if (priv->mm) - mmdrop(priv->mm); + if (priv->lock_ctx.mm) + mmdrop(priv->lock_ctx.mm); return seq_release_private(inode, file); } @@ -610,7 +615,7 @@ static int do_procmap_query(struct proc_maps_private *priv, void __user *uarg) if (!!karg.build_id_size != !!karg.build_id_addr) return -EINVAL; - mm = priv->mm; + mm = priv->lock_ctx.mm; if (!mm || !mmget_not_zero(mm)) return -ESRCH; @@ -1311,7 +1316,7 @@ static int show_smaps_rollup(struct seq_file *m, void *v) { struct proc_maps_private *priv = m->private; struct mem_size_stats mss = {}; - struct mm_struct *mm = priv->mm; + struct mm_struct *mm = priv->lock_ctx.mm; struct vm_area_struct *vma; unsigned long vma_start = 0, last_vma_end = 0; int ret = 0; @@ -1456,9 +1461,9 @@ static int smaps_rollup_open(struct inode *inode, struct file *file) goto out_free; priv->inode = inode; - priv->mm = proc_mem_open(inode, PTRACE_MODE_READ); - if (IS_ERR_OR_NULL(priv->mm)) { - ret = priv->mm ? PTR_ERR(priv->mm) : -ESRCH; + priv->lock_ctx.mm = proc_mem_open(inode, PTRACE_MODE_READ); + if (IS_ERR_OR_NULL(priv->lock_ctx.mm)) { + ret = priv->lock_ctx.mm ? PTR_ERR(priv->lock_ctx.mm) : -ESRCH; single_release(inode, file); goto out_free; @@ -1476,8 +1481,8 @@ static int smaps_rollup_release(struct inode *inode, struct file *file) struct seq_file *seq = file->private_data; struct proc_maps_private *priv = seq->private; - if (priv->mm) - mmdrop(priv->mm); + if (priv->lock_ctx.mm) + mmdrop(priv->lock_ctx.mm); kfree(priv); return single_release(inode, file); diff --git a/fs/proc/task_nommu.c b/fs/proc/task_nommu.c index 59bfd61d653a..d362919f4f68 100644 --- a/fs/proc/task_nommu.c +++ b/fs/proc/task_nommu.c @@ -204,7 +204,7 @@ static void *m_start(struct seq_file *m, loff_t *ppos) if (!priv->task) return ERR_PTR(-ESRCH); - mm = priv->mm; + mm = priv->lock_ctx.mm; if (!mm || !mmget_not_zero(mm)) { put_task_struct(priv->task); priv->task = NULL; @@ -226,7 +226,7 @@ static void *m_start(struct seq_file *m, loff_t *ppos) static void m_stop(struct seq_file *m, void *v) { struct proc_maps_private *priv = m->private; - struct mm_struct *mm = priv->mm; + struct mm_struct *mm = priv->lock_ctx.mm; if (!priv->task) return; @@ -259,9 +259,9 @@ static int maps_open(struct inode *inode, struct file *file, return -ENOMEM; priv->inode = inode; - priv->mm = proc_mem_open(inode, PTRACE_MODE_READ); - if (IS_ERR_OR_NULL(priv->mm)) { - int err = priv->mm ? PTR_ERR(priv->mm) : -ESRCH; + priv->lock_ctx.mm = proc_mem_open(inode, PTRACE_MODE_READ); + if (IS_ERR_OR_NULL(priv->lock_ctx.mm)) { + int err = priv->lock_ctx.mm ? PTR_ERR(priv->lock_ctx.mm) : -ESRCH; seq_release_private(inode, file); return err; @@ -276,8 +276,8 @@ static int map_release(struct inode *inode, struct file *file) struct seq_file *seq = file->private_data; struct proc_maps_private *priv = seq->private; - if (priv->mm) - mmdrop(priv->mm); + if (priv->lock_ctx.mm) + mmdrop(priv->lock_ctx.mm); return seq_release_private(inode, file); } -- 2.50.1.703.g449372360f-goog Utilize per-vma locks to stabilize vma after lookup without taking mmap_lock during PROCMAP_QUERY ioctl execution. If vma lock is contended, we fall back to mmap_lock but take it only momentarily to lock the vma and release the mmap_lock. In a very unlikely case of vm_refcnt overflow, this fall back path will fail and ioctl is done under mmap_lock protection. This change is designed to reduce mmap_lock contention and prevent PROCMAP_QUERY ioctl calls from blocking address space updates. Signed-off-by: Suren Baghdasaryan Acked-by: SeongJae Park --- fs/proc/task_mmu.c | 103 +++++++++++++++++++++++++++++++++++++-------- 1 file changed, 85 insertions(+), 18 deletions(-) diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index c0968d293b61..e64cf40ce9c4 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -132,6 +132,12 @@ static void release_task_mempolicy(struct proc_maps_private *priv) #ifdef CONFIG_PER_VMA_LOCK +static void reset_lock_ctx(struct proc_maps_locking_ctx *lock_ctx) +{ + lock_ctx->locked_vma = NULL; + lock_ctx->mmap_locked = false; +} + static void unlock_ctx_vma(struct proc_maps_locking_ctx *lock_ctx) { if (lock_ctx->locked_vma) { @@ -157,8 +163,7 @@ static inline bool lock_vma_range(struct seq_file *m, lock_ctx->mmap_locked = true; } else { rcu_read_lock(); - lock_ctx->locked_vma = NULL; - lock_ctx->mmap_locked = false; + reset_lock_ctx(lock_ctx); } return true; @@ -522,28 +527,90 @@ static int pid_maps_open(struct inode *inode, struct file *file) PROCMAP_QUERY_VMA_FLAGS \ ) -static int query_vma_setup(struct mm_struct *mm) +#ifdef CONFIG_PER_VMA_LOCK + +static int query_vma_setup(struct proc_maps_locking_ctx *lock_ctx) { - return mmap_read_lock_killable(mm); + reset_lock_ctx(lock_ctx); + + return 0; } -static void query_vma_teardown(struct mm_struct *mm, struct vm_area_struct *vma) +static void query_vma_teardown(struct proc_maps_locking_ctx *lock_ctx) { - mmap_read_unlock(mm); + if (lock_ctx->mmap_locked) { + mmap_read_unlock(lock_ctx->mm); + lock_ctx->mmap_locked = false; + } else { + unlock_ctx_vma(lock_ctx); + } +} + +static struct vm_area_struct *query_vma_find_by_addr(struct proc_maps_locking_ctx *lock_ctx, + unsigned long addr) +{ + struct mm_struct *mm = lock_ctx->mm; + struct vm_area_struct *vma; + struct vma_iterator vmi; + + if (lock_ctx->mmap_locked) + return find_vma(mm, addr); + + /* Unlock previously locked VMA and find the next one under RCU */ + unlock_ctx_vma(lock_ctx); + rcu_read_lock(); + vma_iter_init(&vmi, mm, addr); + vma = lock_next_vma(mm, &vmi, addr); + rcu_read_unlock(); + + if (!vma) + return NULL; + + if (!IS_ERR(vma)) { + lock_ctx->locked_vma = vma; + return vma; + } + + if (PTR_ERR(vma) == -EAGAIN) { + /* Fallback to mmap_lock on vma->vm_refcnt overflow */ + mmap_read_lock(mm); + vma = find_vma(mm, addr); + lock_ctx->mmap_locked = true; + } + + return vma; } -static struct vm_area_struct *query_vma_find_by_addr(struct mm_struct *mm, unsigned long addr) +#else /* CONFIG_PER_VMA_LOCK */ + +static int query_vma_setup(struct proc_maps_locking_ctx *lock_ctx) +{ + return mmap_read_lock_killable(lock_ctx->mm); +} + +static void query_vma_teardown(struct proc_maps_locking_ctx *lock_ctx) +{ + mmap_read_unlock(lock_ctx->mm); +} + +static struct vm_area_struct *query_vma_find_by_addr(struct proc_maps_locking_ctx *lock_ctx, + unsigned long addr) { - return find_vma(mm, addr); + return find_vma(lock_ctx->mm, addr); } -static struct vm_area_struct *query_matching_vma(struct mm_struct *mm, +#endif /* CONFIG_PER_VMA_LOCK */ + +static struct vm_area_struct *query_matching_vma(struct proc_maps_locking_ctx *lock_ctx, unsigned long addr, u32 flags) { struct vm_area_struct *vma; next_vma: - vma = query_vma_find_by_addr(mm, addr); + vma = query_vma_find_by_addr(lock_ctx, addr); + if (IS_ERR(vma)) + return vma; + if (!vma) goto no_vma; @@ -584,11 +651,11 @@ static struct vm_area_struct *query_matching_vma(struct mm_struct *mm, return ERR_PTR(-ENOENT); } -static int do_procmap_query(struct proc_maps_private *priv, void __user *uarg) +static int do_procmap_query(struct mm_struct *mm, void __user *uarg) { + struct proc_maps_locking_ctx lock_ctx = { .mm = mm }; struct procmap_query karg; struct vm_area_struct *vma; - struct mm_struct *mm; const char *name = NULL; char build_id_buf[BUILD_ID_SIZE_MAX], *name_buf = NULL; __u64 usize; @@ -615,17 +682,16 @@ static int do_procmap_query(struct proc_maps_private *priv, void __user *uarg) if (!!karg.build_id_size != !!karg.build_id_addr) return -EINVAL; - mm = priv->lock_ctx.mm; if (!mm || !mmget_not_zero(mm)) return -ESRCH; - err = query_vma_setup(mm); + err = query_vma_setup(&lock_ctx); if (err) { mmput(mm); return err; } - vma = query_matching_vma(mm, karg.query_addr, karg.query_flags); + vma = query_matching_vma(&lock_ctx, karg.query_addr, karg.query_flags); if (IS_ERR(vma)) { err = PTR_ERR(vma); vma = NULL; @@ -710,7 +776,7 @@ static int do_procmap_query(struct proc_maps_private *priv, void __user *uarg) } /* unlock vma or mmap_lock, and put mm_struct before copying data to user */ - query_vma_teardown(mm, vma); + query_vma_teardown(&lock_ctx); mmput(mm); if (karg.vma_name_size && copy_to_user(u64_to_user_ptr(karg.vma_name_addr), @@ -730,7 +796,7 @@ static int do_procmap_query(struct proc_maps_private *priv, void __user *uarg) return 0; out: - query_vma_teardown(mm, vma); + query_vma_teardown(&lock_ctx); mmput(mm); kfree(name_buf); return err; @@ -743,7 +809,8 @@ static long procfs_procmap_ioctl(struct file *file, unsigned int cmd, unsigned l switch (cmd) { case PROCMAP_QUERY: - return do_procmap_query(priv, (void __user *)arg); + /* priv->lock_ctx.mm is set during file open operation */ + return do_procmap_query(priv->lock_ctx.mm, (void __user *)arg); default: return -ENOIOCTLCMD; } -- 2.50.1.703.g449372360f-goog