On Mon, Jun 01, 2020 at 01:05:43PM -0700, Eric Biggers wrote:
From: Eric Biggers ebiggers@google.com
If the dentry name passed to ->d_compare() fits in dentry::d_iname, then it may be concurrently modified by a rename. This can cause undefined behavior (possibly out-of-bounds memory accesses or crashes) in utf8_strncasecmp(), since fs/unicode/ isn't written to handle strings that may be concurrently modified.
Fix this by first copying the filename to a stack buffer if needed. This way we get a stable snapshot of the filename.
Fixes: b886ee3e778e ("ext4: Support case-insensitive file name lookups") Cc: stable@vger.kernel.org # v5.2+ Cc: Al Viro viro@zeniv.linux.org.uk Cc: Daniel Rosenberg drosen@google.com Cc: Gabriel Krisman Bertazi krisman@collabora.co.uk Signed-off-by: Eric Biggers ebiggers@google.com
v2: use memcpy() + barrier() instead of a byte-by-byte copy.
fs/ext4/dir.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)
Ted, could you take this through the ext4 tree as a fix for 5.8? The f2fs patch has been merged already.
- Eric