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authorCyrill Gorcunov <gorcunov@openvz.org>2012-05-17 17:03:25 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-05-17 18:00:51 -0700
commiteb94cd96e05d6c65a07937e66a04ea265c1b767d (patch)
tree0432ec8db57798b5212fa2200fe1293b01bd3361
parentc0a5f4a05af588a0f9951f8d24e2564b09501918 (diff)
downloadlinux-stericsson-eb94cd96e05d6c65a07937e66a04ea265c1b767d.tar.gz
fs, proc: fix ABBA deadlock in case of execution attempt of map_files/ entries
map_files/ entries are never supposed to be executed, still curious minds might try to run them, which leads to the following deadlock ====================================================== [ INFO: possible circular locking dependency detected ] 3.4.0-rc4-24406-g841e6a6 #121 Not tainted ------------------------------------------------------- bash/1556 is trying to acquire lock: (&sb->s_type->i_mutex_key#8){+.+.+.}, at: do_lookup+0x267/0x2b1 but task is already holding lock: (&sig->cred_guard_mutex){+.+.+.}, at: prepare_bprm_creds+0x2d/0x69 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&sig->cred_guard_mutex){+.+.+.}: validate_chain+0x444/0x4f4 __lock_acquire+0x387/0x3f8 lock_acquire+0x12b/0x158 __mutex_lock_common+0x56/0x3a9 mutex_lock_killable_nested+0x40/0x45 lock_trace+0x24/0x59 proc_map_files_lookup+0x5a/0x165 __lookup_hash+0x52/0x73 do_lookup+0x276/0x2b1 walk_component+0x3d/0x114 do_last+0xfc/0x540 path_openat+0xd3/0x306 do_filp_open+0x3d/0x89 do_sys_open+0x74/0x106 sys_open+0x21/0x23 tracesys+0xdd/0xe2 -> #0 (&sb->s_type->i_mutex_key#8){+.+.+.}: check_prev_add+0x6a/0x1ef validate_chain+0x444/0x4f4 __lock_acquire+0x387/0x3f8 lock_acquire+0x12b/0x158 __mutex_lock_common+0x56/0x3a9 mutex_lock_nested+0x40/0x45 do_lookup+0x267/0x2b1 walk_component+0x3d/0x114 link_path_walk+0x1f9/0x48f path_openat+0xb6/0x306 do_filp_open+0x3d/0x89 open_exec+0x25/0xa0 do_execve_common+0xea/0x2f9 do_execve+0x43/0x45 sys_execve+0x43/0x5a stub_execve+0x6c/0xc0 This is because prepare_bprm_creds grabs task->signal->cred_guard_mutex and when do_lookup happens we try to grab task->signal->cred_guard_mutex again in lock_trace. Fix it using plain ptrace_may_access() helper in proc_map_files_lookup() and in proc_map_files_readdir() instead of lock_trace(), the caller must be CAP_SYS_ADMIN granted anyway. Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org> Reported-by: Sasha Levin <levinsasha928@gmail.com> Cc: Konstantin Khlebnikov <khlebnikov@openvz.org> Cc: Pavel Emelyanov <xemul@openvz.org> Cc: Dave Jones <davej@redhat.com> Cc: Vasiliy Kulikov <segoon@openwall.com> Cc: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/proc/base.c20
1 files changed, 8 insertions, 12 deletions
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 1c8b280146d7..8e139c90f9fd 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2177,16 +2177,16 @@ static struct dentry *proc_map_files_lookup(struct inode *dir,
goto out;
result = ERR_PTR(-EACCES);
- if (lock_trace(task))
+ if (!ptrace_may_access(task, PTRACE_MODE_READ))
goto out_put_task;
result = ERR_PTR(-ENOENT);
if (dname_to_vma_addr(dentry, &vm_start, &vm_end))
- goto out_unlock;
+ goto out_put_task;
mm = get_task_mm(task);
if (!mm)
- goto out_unlock;
+ goto out_put_task;
down_read(&mm->mmap_sem);
vma = find_exact_vma(mm, vm_start, vm_end);
@@ -2198,8 +2198,6 @@ static struct dentry *proc_map_files_lookup(struct inode *dir,
out_no_vma:
up_read(&mm->mmap_sem);
mmput(mm);
-out_unlock:
- unlock_trace(task);
out_put_task:
put_task_struct(task);
out:
@@ -2233,7 +2231,7 @@ proc_map_files_readdir(struct file *filp, void *dirent, filldir_t filldir)
goto out;
ret = -EACCES;
- if (lock_trace(task))
+ if (!ptrace_may_access(task, PTRACE_MODE_READ))
goto out_put_task;
ret = 0;
@@ -2241,12 +2239,12 @@ proc_map_files_readdir(struct file *filp, void *dirent, filldir_t filldir)
case 0:
ino = inode->i_ino;
if (filldir(dirent, ".", 1, 0, ino, DT_DIR) < 0)
- goto out_unlock;
+ goto out_put_task;
filp->f_pos++;
case 1:
ino = parent_ino(dentry);
if (filldir(dirent, "..", 2, 1, ino, DT_DIR) < 0)
- goto out_unlock;
+ goto out_put_task;
filp->f_pos++;
default:
{
@@ -2257,7 +2255,7 @@ proc_map_files_readdir(struct file *filp, void *dirent, filldir_t filldir)
mm = get_task_mm(task);
if (!mm)
- goto out_unlock;
+ goto out_put_task;
down_read(&mm->mmap_sem);
nr_files = 0;
@@ -2287,7 +2285,7 @@ proc_map_files_readdir(struct file *filp, void *dirent, filldir_t filldir)
flex_array_free(fa);
up_read(&mm->mmap_sem);
mmput(mm);
- goto out_unlock;
+ goto out_put_task;
}
for (i = 0, vma = mm->mmap, pos = 2; vma;
vma = vma->vm_next) {
@@ -2332,8 +2330,6 @@ proc_map_files_readdir(struct file *filp, void *dirent, filldir_t filldir)
}
}
-out_unlock:
- unlock_trace(task);
out_put_task:
put_task_struct(task);
out: