From: Theodore Ts'o Date: Tue, 25 Dec 2018 05:56:33 +0000 (-0500) Subject: ext4: fix a potential fiemap/page fault deadlock w/ inline_data X-Git-Tag: v4.14.94~6 X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=b4727299f58df8c7feaac247f7b841b610b5cbaf;p=users%2Fjedix%2Flinux-maple.git ext4: fix a potential fiemap/page fault deadlock w/ inline_data commit 2b08b1f12cd664dc7d5c84ead9ff25ae97ad5491 upstream. The ext4_inline_data_fiemap() function calls fiemap_fill_next_extent() while still holding the xattr semaphore. This is not necessary and it triggers a circular lockdep warning. This is because fiemap_fill_next_extent() could trigger a page fault when it writes into page which triggers a page fault. If that page is mmaped from the inline file in question, this could very well result in a deadlock. This problem can be reproduced using generic/519 with a file system configuration which has the inline_data feature enabled. Signed-off-by: Theodore Ts'o Cc: stable@kernel.org Signed-off-by: Greg Kroah-Hartman --- diff --git a/fs/ext4/inline.c b/fs/ext4/inline.c index 40a2d1a428c2..137c752ab985 100644 --- a/fs/ext4/inline.c +++ b/fs/ext4/inline.c @@ -1864,12 +1864,12 @@ int ext4_inline_data_fiemap(struct inode *inode, physical += (char *)ext4_raw_inode(&iloc) - iloc.bh->b_data; physical += offsetof(struct ext4_inode, i_block); - if (physical) - error = fiemap_fill_next_extent(fieinfo, start, physical, - inline_len, flags); brelse(iloc.bh); out: up_read(&EXT4_I(inode)->xattr_sem); + if (physical) + error = fiemap_fill_next_extent(fieinfo, start, physical, + inline_len, flags); return (error < 0 ? error : 0); }