From 4a3674acbf8b076bb42b68f5d95f0877acabf210 Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Wed, 18 Apr 2018 11:49:31 -0400 Subject: ext4: set h_journal if there is a failure starting a reserved handle commit b2569260d55228b617bd82aba6d0db2faeeb4116 upstream. If ext4 tries to start a reserved handle via jbd2_journal_start_reserved(), and the journal has been aborted, this can result in a NULL pointer dereference. This is because the fields h_journal and h_transaction in the handle structure share the same memory, via a union, so jbd2_journal_start_reserved() will clear h_journal before calling start_this_handle(). If this function fails due to an aborted handle, h_journal will still be NULL, and the call to jbd2_journal_free_reserved() will pass a NULL journal to sub_reserve_credits(). This can be reproduced by running "kvm-xfstests -c dioread_nolock generic/475". Cc: stable@kernel.org # 3.11 Fixes: 8f7d89f36829b ("jbd2: transaction reservation support") Signed-off-by: Theodore Ts'o Reviewed-by: Andreas Dilger Reviewed-by: Jan Kara Signed-off-by: Greg Kroah-Hartman --- fs/jbd2/transaction.c | 1 + 1 file changed, 1 insertion(+) (limited to 'fs/jbd2') diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c index c0681814c379..07793e25c976 100644 --- a/fs/jbd2/transaction.c +++ b/fs/jbd2/transaction.c @@ -535,6 +535,7 @@ int jbd2_journal_start_reserved(handle_t *handle, unsigned int type, */ ret = start_this_handle(journal, handle, GFP_NOFS); if (ret < 0) { + handle->h_journal = journal; jbd2_journal_free_reserved(handle); return ret; } -- cgit v1.2.3