This function is used by ptrace and proc files like /proc/pid/cmdline and /proc/pid/environ. Return 0 (bytes read) if current task is killed.
Mmap_sem could be locked for a long time or forever if something wrong. Signed-off-by: Konstantin Khlebnikov <[email protected]> --- mm/memory.c | 4 +++- mm/nommu.c | 3 ++- 2 files changed, 5 insertions(+), 2 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 96f1d473c89a..2e6846d09023 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4348,7 +4348,9 @@ int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm, void *old_buf = buf; int write = gup_flags & FOLL_WRITE; - down_read(&mm->mmap_sem); + if (down_read_killable(&mm->mmap_sem)) + return 0; + /* ignore errors, just check how much was successfully transferred */ while (len) { int bytes, ret, offset; diff --git a/mm/nommu.c b/mm/nommu.c index b492fd1fcf9f..cad8fb34088f 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -1791,7 +1791,8 @@ int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm, struct vm_area_struct *vma; int write = gup_flags & FOLL_WRITE; - down_read(&mm->mmap_sem); + if (down_read_killable(&mm->mmap_sem)) + return 0; /* the access must start within one of the target process's mappings */ vma = find_vma(mm, addr);
