From: Al Viro viro@zeniv.linux.org.uk

butt3rflyh4ck reported memory leak found by syzkaller.

A param->string held by exfat_mount_options.

BUG: memory leak

unreferenced object 0xffff88801972e090 (size 8): comm "syz-executor.2", pid 16298, jiffies 4295172466 (age 14.060s) hex dump (first 8 bytes): 6b 6f 69 38 2d 75 00 00 koi8-u.. backtrace: [<000000005bfe35d6>] kstrdup+0x36/0x70 mm/util.c:60 [<0000000018ed3277>] exfat_parse_param+0x160/0x5e0 fs/exfat/super.c:276 [<000000007680462b>] vfs_parse_fs_param+0x2b4/0x610 fs/fs_context.c:147 [<0000000097c027f2>] vfs_parse_fs_string+0xe6/0x150 fs/fs_context.c:191 [<00000000371bf78f>] generic_parse_monolithic+0x16f/0x1f0 fs/fs_context.c:231 [<000000005ce5eb1b>] do_new_mount fs/namespace.c:2812 [inline] [<000000005ce5eb1b>] do_mount+0x12bb/0x1b30 fs/namespace.c:3141 [<00000000b642040c>] __do_sys_mount fs/namespace.c:3350 [inline] [<00000000b642040c>] __se_sys_mount fs/namespace.c:3327 [inline] [<00000000b642040c>] __x64_sys_mount+0x18f/0x230 fs/namespace.c:3327 [<000000003b024e98>] do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295 [<00000000ce2b698c>] entry_SYSCALL_64_after_hwframe+0x49/0xb3

exfat_free() should call exfat_free_iocharset(), to prevent a leak in case we fail after parsing iocharset= but before calling get_tree_bdev().

Additionally, there's no point copying param->string in exfat_parse_param() - just steal it, leaving NULL in param->string. That's independent from the leak or fix thereof - it's simply avoiding an extra copy.

Fixes: 719c1e182916 ("exfat: add super block operations") Cc: stable@vger.kernel.org # v5.7 Reported-by: butt3rflyh4ck butterflyhuangxx@gmail.com Signed-off-by: Al Viro viro@zeniv.linux.org.uk --- v2: - update patch description in more detail.

fs/exfat/super.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/fs/exfat/super.c b/fs/exfat/super.c index 405717e4e3ea..e650e65536f8 100644 --- a/fs/exfat/super.c +++ b/fs/exfat/super.c @@ -273,9 +273,8 @@ static int exfat_parse_param(struct fs_context *fc, struct fs_parameter *param) break; case Opt_charset: exfat_free_iocharset(sbi); - opts->iocharset = kstrdup(param->string, GFP_KERNEL); - if (!opts->iocharset) - return -ENOMEM; + opts->iocharset = param->string; + param->string = NULL; break; case Opt_errors: opts->errors = result.uint_32; @@ -686,7 +685,12 @@ static int exfat_get_tree(struct fs_context *fc)

static void exfat_free(struct fs_context *fc) { - kfree(fc->s_fs_info); + struct exfat_sb_info *sbi = fc->s_fs_info; + + if (sbi) { + exfat_free_iocharset(sbi); + kfree(sbi); + } }

static const struct fs_context_operations exfat_context_ops = {