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x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit ARC-Authentication-Results: i=1; imf03.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=ReshceG5; spf=pass (imf03.hostedemail.com: domain of akpm@linux-foundation.org designates 145.40.68.75 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1666384913; a=rsa-sha256; cv=none; b=6Y5cusAA6CT6G/KxKNA9yijENXwDh5f0HXrHbuUm2z2lDmkbY14vwnMYyAyFxg9UW3vpmM hozgKExQiH+30FeU0raRIt1Y8LxjRIk5kyHy2CXIctw1MNrZ5oKpmfSr1+IK1x3he4QFAf A8unx4BII4eyzi32Zgj8Q5bloP9X1uo= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1666384913; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=Y+68vsZsCWyDtWv8Ty+HtYwun7tVR912tJZjFq4zMno=; b=i9cL3qDhnTlnLutAFEvERvsaLpINCDRoEXzy7MzCTIgioUKSMFsnTBqTGgnIc0YZqFC45D vVMQzobWR2q0MIvb/DZy8m4pVIfHz38OerOrrhAtcSoWolJpXNySvDtAGA+Wn5G/03KzrM FlZYYlfuDG47JDJOta0hrSS4AqGZU7A= X-Rspamd-Queue-Id: 201A92002D X-Rspam-User: Authentication-Results: imf03.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=ReshceG5; spf=pass (imf03.hostedemail.com: domain of akpm@linux-foundation.org designates 145.40.68.75 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none X-Rspamd-Server: rspam11 X-Stat-Signature: 6ggpf1gxzbj4d18y1tagb1o6zz9bee6y X-HE-Tag: 1666384912-995049 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, 20 Oct 2022 16:38:18 -0700 Mike Kravetz wrote: > On 10/21/22 07:16, Hawkins Jiawei wrote: > > Syzkaller reports a null-ptr-deref bug as follows: > > ====================================================== > > KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] > > RIP: 0010:hugetlbfs_parse_param+0x1dd/0x8e0 fs/hugetlbfs/inode.c:1380 > > [...] > > Call Trace: > > > > vfs_parse_fs_param fs/fs_context.c:148 [inline] > > vfs_parse_fs_param+0x1f9/0x3c0 fs/fs_context.c:129 > > vfs_parse_fs_string+0xdb/0x170 fs/fs_context.c:191 > > generic_parse_monolithic+0x16f/0x1f0 fs/fs_context.c:231 > > do_new_mount fs/namespace.c:3036 [inline] > > path_mount+0x12de/0x1e20 fs/namespace.c:3370 > > do_mount fs/namespace.c:3383 [inline] > > __do_sys_mount fs/namespace.c:3591 [inline] > > __se_sys_mount fs/namespace.c:3568 [inline] > > __x64_sys_mount+0x27f/0x300 fs/namespace.c:3568 > > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > > do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 > > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > [...] > > > > ====================================================== > > > > According to commit > > ac369cdd9448("vfs: parse: deal with zero length string value"), > > kernel will sets the param->string to null pointer in > > vfs_parse_fs_string() if fs string has zero length. > > > > Yet the problem is that, hugetlbfs_parse_param() will > > dereference the param->string, without checking whether it > > is a null pointer. To be more specific, if hugetlbfs_parse_param() > > parses an illegal mount parameter, such as "size=,", kernel will > > constructs struct fs_parameter with null pointer in > > vfs_parse_fs_string(), then passes this struct fs_parameter to > > hugetlbfs_parse_param(), which triggers the above > > null-ptr-deref bug. > > > > This patch solves it by adding sanity check on param->string > > in hugetlbfs_parse_param(). > > > > Reported-by: syzbot+a3e6acd85ded5c16a709@syzkaller.appspotmail.com > > Tested-by: syzbot+a3e6acd85ded5c16a709@syzkaller.appspotmail.com > > Link: https://lore.kernel.org/all/0000000000005ad00405eb7148c6@google.com/ > > Signed-off-by: Hawkins Jiawei > > Thank you! > > This was on my list of things to look at. > > Do you know if the issue existed before commit ac369cdd9448? Just > wondering if we need a Fixes tag and stable backports. Ian Kent's "vfs: parse: deal with zero length string value" exists only in mm-nonmm-unstable. I'm hoping that it gets some attention from Al Viro. I'll merge this patch so we're ready for Ian's patch. I normally merge mm-stable ahead of mm-nonmm-stable so there shouldn't be a bisection window. Ian, could you please go through the filesystems and see if there are other instances of this getting ready to bite us? > I'll take a closer look at the patch a bit later, unless someone beats > me to it. > -- > Mike Kravetz > > > --- > > fs/hugetlbfs/inode.c | 6 +++--- > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c > > index 7f836f8f9db1..3ee84604e36d 100644 > > --- a/fs/hugetlbfs/inode.c > > +++ b/fs/hugetlbfs/inode.c > > @@ -1377,7 +1377,7 @@ static int hugetlbfs_parse_param(struct fs_context *fc, struct fs_parameter *par > > > > case Opt_size: > > /* memparse() will accept a K/M/G without a digit */ > > - if (!isdigit(param->string[0])) > > + if (!param->string || !isdigit(param->string[0])) > > goto bad_val; > > ctx->max_size_opt = memparse(param->string, &rest); > > ctx->max_val_type = SIZE_STD; > > @@ -1387,7 +1387,7 @@ static int hugetlbfs_parse_param(struct fs_context *fc, struct fs_parameter *par > > > > case Opt_nr_inodes: > > /* memparse() will accept a K/M/G without a digit */ > > - if (!isdigit(param->string[0])) > > + if (!param->string || !isdigit(param->string[0])) > > goto bad_val; > > ctx->nr_inodes = memparse(param->string, &rest); > > return 0; > > @@ -1403,7 +1403,7 @@ static int hugetlbfs_parse_param(struct fs_context *fc, struct fs_parameter *par > > > > case Opt_min_size: > > /* memparse() will accept a K/M/G without a digit */ > > - if (!isdigit(param->string[0])) > > + if (!param->string || !isdigit(param->string[0])) > > goto bad_val; > > ctx->min_size_opt = memparse(param->string, &rest); > > ctx->min_val_type = SIZE_STD; > > -- > > 2.25.1 > >