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-rw-r--r--fs/read_write.c13
1 files changed, 13 insertions, 0 deletions
diff --git a/fs/read_write.c b/fs/read_write.c
index 969a6d9c020b..5cc6924eb158 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -50,6 +50,14 @@ generic_file_llseek_unlocked(struct file *file, loff_t offset, int origin)
offset += inode->i_size;
break;
case SEEK_CUR:
+ /*
+ * Here we special-case the lseek(fd, 0, SEEK_CUR)
+ * position-querying operation. Avoid rewriting the "same"
+ * f_pos value back to the file because a concurrent read(),
+ * write() or lseek() might have altered it
+ */
+ if (offset == 0)
+ return file->f_pos;
offset += file->f_pos;
break;
}
@@ -105,6 +113,10 @@ loff_t default_llseek(struct file *file, loff_t offset, int origin)
offset += i_size_read(file->f_path.dentry->d_inode);
break;
case SEEK_CUR:
+ if (offset == 0) {
+ retval = file->f_pos;
+ goto out;
+ }
offset += file->f_pos;
}
retval = -EINVAL;
@@ -115,6 +127,7 @@ loff_t default_llseek(struct file *file, loff_t offset, int origin)
}
retval = offset;
}
+out:
unlock_kernel();
return retval;
}