fsioctl.c: make generic_block_fiemap() signal-tolerant
__generic_block_fiemap may spin very long time for large sparse files.
Without this patch an unprivileged user may abuse system resources simply
by spawning a vast number of unkilable busyloops (works on ext2/ext3):
truncate --size 1T test
for ((i=0;i<1024;i++))
do
filefrag test > /dev/null &
done
Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/Documentation/filesystems/fiemap.txt b/Documentation/filesystems/fiemap.txt
index 1b805a0..f6d9c99 100644
--- a/Documentation/filesystems/fiemap.txt
+++ b/Documentation/filesystems/fiemap.txt
@@ -196,7 +196,8 @@
};
It is intended that the file system should not need to access any of this
-structure directly.
+structure directly. Filesystem handlers should be tolerant to signals and return
+EINTR once fatal signal received.
Flag checking should be done at the beginning of the ->fiemap callback via the
diff --git a/fs/ioctl.c b/fs/ioctl.c
index 214c3c1..5d01d26 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -379,6 +379,11 @@
past_eof = true;
}
cond_resched();
+ if (fatal_signal_pending(current)) {
+ ret = -EINTR;
+ break;
+ }
+
} while (1);
/* If ret is 1 then we just hit the end of the extent array */
