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[PATCH] fix file and descriptor handling in perfmon
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Races galore...  General rule: as soon as it's in descriptor table,
it's over; another thread might have started IO on it/dup2() it
elsewhere/dup2() something *over* it/etc.  fd_install() is the very
last step one should take - it's a point of no return.

Besides, the damn thing leaked on failure exits...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Al Viro committed May 1, 2008
1 parent e4c576b commit 74d92ab
Showing 1 changed file with 87 additions and 112 deletions.
199 changes: 87 additions & 112 deletions arch/ia64/kernel/perfmon.c
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Original file line number Diff line number Diff line change
Expand Up @@ -867,7 +867,7 @@ pfm_rvfree(void *mem, unsigned long size)
}

static pfm_context_t *
pfm_context_alloc(void)
pfm_context_alloc(int ctx_flags)
{
pfm_context_t *ctx;

Expand All @@ -878,6 +878,46 @@ pfm_context_alloc(void)
ctx = kzalloc(sizeof(pfm_context_t), GFP_KERNEL);
if (ctx) {
DPRINT(("alloc ctx @%p\n", ctx));

/*
* init context protection lock
*/
spin_lock_init(&ctx->ctx_lock);

/*
* context is unloaded
*/
ctx->ctx_state = PFM_CTX_UNLOADED;

/*
* initialization of context's flags
*/
ctx->ctx_fl_block = (ctx_flags & PFM_FL_NOTIFY_BLOCK) ? 1 : 0;
ctx->ctx_fl_system = (ctx_flags & PFM_FL_SYSTEM_WIDE) ? 1: 0;
ctx->ctx_fl_no_msg = (ctx_flags & PFM_FL_OVFL_NO_MSG) ? 1: 0;
/*
* will move to set properties
* ctx->ctx_fl_excl_idle = (ctx_flags & PFM_FL_EXCL_IDLE) ? 1: 0;
*/

/*
* init restart semaphore to locked
*/
init_completion(&ctx->ctx_restart_done);

/*
* activation is used in SMP only
*/
ctx->ctx_last_activation = PFM_INVALID_ACTIVATION;
SET_LAST_CPU(ctx, -1);

/*
* initialize notification message queue
*/
ctx->ctx_msgq_head = ctx->ctx_msgq_tail = 0;
init_waitqueue_head(&ctx->ctx_msgq_wait);
init_waitqueue_head(&ctx->ctx_zombieq);

}
return ctx;
}
Expand Down Expand Up @@ -2165,28 +2205,21 @@ static struct dentry_operations pfmfs_dentry_operations = {
};


static int
pfm_alloc_fd(struct file **cfile)
static struct file *
pfm_alloc_file(pfm_context_t *ctx)
{
int fd, ret = 0;
struct file *file = NULL;
struct inode * inode;
struct file *file;
struct inode *inode;
struct dentry *dentry;
char name[32];
struct qstr this;

fd = get_unused_fd();
if (fd < 0) return -ENFILE;

ret = -ENFILE;

file = get_empty_filp();
if (!file) goto out;

/*
* allocate a new inode
*/
inode = new_inode(pfmfs_mnt->mnt_sb);
if (!inode) goto out;
if (!inode)
return ERR_PTR(-ENOMEM);

DPRINT(("new inode ino=%ld @%p\n", inode->i_ino, inode));

Expand All @@ -2199,59 +2232,28 @@ pfm_alloc_fd(struct file **cfile)
this.len = strlen(name);
this.hash = inode->i_ino;

ret = -ENOMEM;

/*
* allocate a new dcache entry
*/
file->f_path.dentry = d_alloc(pfmfs_mnt->mnt_sb->s_root, &this);
if (!file->f_path.dentry) goto out;
dentry = d_alloc(pfmfs_mnt->mnt_sb->s_root, &this);
if (!dentry) {
iput(inode);
return ERR_PTR(-ENOMEM);
}

file->f_path.dentry->d_op = &pfmfs_dentry_operations;
dentry->d_op = &pfmfs_dentry_operations;
d_add(dentry, inode);

d_add(file->f_path.dentry, inode);
file->f_path.mnt = mntget(pfmfs_mnt);
file->f_mapping = inode->i_mapping;
file = alloc_file(pfmfs_mnt, dentry, FMODE_READ, &pfm_file_ops);
if (!file) {
dput(dentry);
return ERR_PTR(-ENFILE);
}

file->f_op = &pfm_file_ops;
file->f_mode = FMODE_READ;
file->f_flags = O_RDONLY;
file->f_pos = 0;

/*
* may have to delay until context is attached?
*/
fd_install(fd, file);

/*
* the file structure we will use
*/
*cfile = file;

return fd;
out:
if (file) put_filp(file);
put_unused_fd(fd);
return ret;
}

static void
pfm_free_fd(int fd, struct file *file)
{
struct files_struct *files = current->files;
struct fdtable *fdt;
file->private_data = ctx;

/*
* there ie no fd_uninstall(), so we do it here
*/
spin_lock(&files->file_lock);
fdt = files_fdtable(files);
rcu_assign_pointer(fdt->fd[fd], NULL);
spin_unlock(&files->file_lock);

if (file)
put_filp(file);
put_unused_fd(fd);
return file;
}

static int
Expand Down Expand Up @@ -2475,6 +2477,7 @@ pfm_setup_buffer_fmt(struct task_struct *task, struct file *filp, pfm_context_t

/* link buffer format and context */
ctx->ctx_buf_fmt = fmt;
ctx->ctx_fl_is_sampling = 1; /* assume record() is defined */

/*
* check if buffer format wants to use perfmon buffer allocation/mapping service
Expand Down Expand Up @@ -2669,78 +2672,45 @@ pfm_context_create(pfm_context_t *ctx, void *arg, int count, struct pt_regs *reg
{
pfarg_context_t *req = (pfarg_context_t *)arg;
struct file *filp;
struct path path;
int ctx_flags;
int fd;
int ret;

/* let's check the arguments first */
ret = pfarg_is_sane(current, req);
if (ret < 0) return ret;
if (ret < 0)
return ret;

ctx_flags = req->ctx_flags;

ret = -ENOMEM;

ctx = pfm_context_alloc();
if (!ctx) goto error;
fd = get_unused_fd();
if (fd < 0)
return fd;

ret = pfm_alloc_fd(&filp);
if (ret < 0) goto error_file;
ctx = pfm_context_alloc(ctx_flags);
if (!ctx)
goto error;

req->ctx_fd = ctx->ctx_fd = ret;
filp = pfm_alloc_file(ctx);
if (IS_ERR(filp)) {
ret = PTR_ERR(filp);
goto error_file;
}

/*
* attach context to file
*/
filp->private_data = ctx;
req->ctx_fd = ctx->ctx_fd = fd;

/*
* does the user want to sample?
*/
if (pfm_uuid_cmp(req->ctx_smpl_buf_id, pfm_null_uuid)) {
ret = pfm_setup_buffer_fmt(current, filp, ctx, ctx_flags, 0, req);
if (ret) goto buffer_error;
if (ret)
goto buffer_error;
}

/*
* init context protection lock
*/
spin_lock_init(&ctx->ctx_lock);

/*
* context is unloaded
*/
ctx->ctx_state = PFM_CTX_UNLOADED;

/*
* initialization of context's flags
*/
ctx->ctx_fl_block = (ctx_flags & PFM_FL_NOTIFY_BLOCK) ? 1 : 0;
ctx->ctx_fl_system = (ctx_flags & PFM_FL_SYSTEM_WIDE) ? 1: 0;
ctx->ctx_fl_is_sampling = ctx->ctx_buf_fmt ? 1 : 0; /* assume record() is defined */
ctx->ctx_fl_no_msg = (ctx_flags & PFM_FL_OVFL_NO_MSG) ? 1: 0;
/*
* will move to set properties
* ctx->ctx_fl_excl_idle = (ctx_flags & PFM_FL_EXCL_IDLE) ? 1: 0;
*/

/*
* init restart semaphore to locked
*/
init_completion(&ctx->ctx_restart_done);

/*
* activation is used in SMP only
*/
ctx->ctx_last_activation = PFM_INVALID_ACTIVATION;
SET_LAST_CPU(ctx, -1);

/*
* initialize notification message queue
*/
ctx->ctx_msgq_head = ctx->ctx_msgq_tail = 0;
init_waitqueue_head(&ctx->ctx_msgq_wait);
init_waitqueue_head(&ctx->ctx_zombieq);

DPRINT(("ctx=%p flags=0x%x system=%d notify_block=%d excl_idle=%d no_msg=%d ctx_fd=%d \n",
ctx,
ctx_flags,
Expand All @@ -2755,10 +2725,14 @@ pfm_context_create(pfm_context_t *ctx, void *arg, int count, struct pt_regs *reg
*/
pfm_reset_pmu_state(ctx);

fd_install(fd, filp);

return 0;

buffer_error:
pfm_free_fd(ctx->ctx_fd, filp);
path = filp->f_path;
put_filp(filp);
path_put(&path);

if (ctx->ctx_buf_fmt) {
pfm_buf_fmt_exit(ctx->ctx_buf_fmt, current, NULL, regs);
Expand All @@ -2767,6 +2741,7 @@ pfm_context_create(pfm_context_t *ctx, void *arg, int count, struct pt_regs *reg
pfm_context_free(ctx);

error:
put_unused_fd(fd);
return ret;
}

Expand Down

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