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author | Baokun Li <libaokun1@huawei.com> | 2024-09-27 21:33:29 +0800 |
---|---|---|
committer | Theodore Ts'o <tytso@mit.edu> | 2024-10-04 17:36:28 -0400 |
commit | 6121258c2b33ceac3d21f6a221452692c465df88 (patch) | |
tree | bb273ab1f3e5f16a3ab3cd2c88c945bce379f9ab | |
parent | 04e6ce8f06d161399e5afde3df5dcfa9455b4952 (diff) | |
download | lwn-6121258c2b33ceac3d21f6a221452692c465df88.tar.gz lwn-6121258c2b33ceac3d21f6a221452692c465df88.zip |
ext4: fix off by one issue in alloc_flex_gd()
Wesley reported an issue:
==================================================================
EXT4-fs (dm-5): resizing filesystem from 7168 to 786432 blocks
------------[ cut here ]------------
kernel BUG at fs/ext4/resize.c:324!
CPU: 9 UID: 0 PID: 3576 Comm: resize2fs Not tainted 6.11.0+ #27
RIP: 0010:ext4_resize_fs+0x1212/0x12d0
Call Trace:
__ext4_ioctl+0x4e0/0x1800
ext4_ioctl+0x12/0x20
__x64_sys_ioctl+0x99/0xd0
x64_sys_call+0x1206/0x20d0
do_syscall_64+0x72/0x110
entry_SYSCALL_64_after_hwframe+0x76/0x7e
==================================================================
While reviewing the patch, Honza found that when adjusting resize_bg in
alloc_flex_gd(), it was possible for flex_gd->resize_bg to be bigger than
flexbg_size.
The reproduction of the problem requires the following:
o_group = flexbg_size * 2 * n;
o_size = (o_group + 1) * group_size;
n_group: [o_group + flexbg_size, o_group + flexbg_size * 2)
o_size = (n_group + 1) * group_size;
Take n=0,flexbg_size=16 as an example:
last:15
|o---------------|--------------n-|
o_group:0 resize to n_group:30
The corresponding reproducer is:
img=test.img
rm -f $img
truncate -s 600M $img
mkfs.ext4 -F $img -b 1024 -G 16 8M
dev=`losetup -f --show $img`
mkdir -p /tmp/test
mount $dev /tmp/test
resize2fs $dev 248M
Delete the problematic plus 1 to fix the issue, and add a WARN_ON_ONCE()
to prevent the issue from happening again.
[ Note: another reproucer which this commit fixes is:
img=test.img
rm -f $img
truncate -s 25MiB $img
mkfs.ext4 -b 4096 -E nodiscard,lazy_itable_init=0,lazy_journal_init=0 $img
truncate -s 3GiB $img
dev=`losetup -f --show $img`
mkdir -p /tmp/test
mount $dev /tmp/test
resize2fs $dev 3G
umount $dev
losetup -d $dev
-- TYT ]
Reported-by: Wesley Hershberger <wesley.hershberger@canonical.com>
Closes: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2081231
Reported-by: Stéphane Graber <stgraber@stgraber.org>
Closes: https://lore.kernel.org/all/20240925143325.518508-1-aleksandr.mikhalitsyn@canonical.com/
Tested-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Tested-by: Eric Sandeen <sandeen@redhat.com>
Fixes: 665d3e0af4d3 ("ext4: reduce unnecessary memory allocation in alloc_flex_gd()")
Cc: stable@vger.kernel.org
Signed-off-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20240927133329.1015041-1-libaokun@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
-rw-r--r-- | fs/ext4/resize.c | 18 |
1 files changed, 10 insertions, 8 deletions
diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c index e04eb08b9060..a2704f064361 100644 --- a/fs/ext4/resize.c +++ b/fs/ext4/resize.c @@ -230,8 +230,8 @@ struct ext4_new_flex_group_data { #define MAX_RESIZE_BG 16384 /* - * alloc_flex_gd() allocates a ext4_new_flex_group_data with size of - * @flexbg_size. + * alloc_flex_gd() allocates an ext4_new_flex_group_data that satisfies the + * resizing from @o_group to @n_group, its size is typically @flexbg_size. * * Returns NULL on failure otherwise address of the allocated structure. */ @@ -239,25 +239,27 @@ static struct ext4_new_flex_group_data *alloc_flex_gd(unsigned int flexbg_size, ext4_group_t o_group, ext4_group_t n_group) { ext4_group_t last_group; + unsigned int max_resize_bg; struct ext4_new_flex_group_data *flex_gd; flex_gd = kmalloc(sizeof(*flex_gd), GFP_NOFS); if (flex_gd == NULL) goto out3; - if (unlikely(flexbg_size > MAX_RESIZE_BG)) - flex_gd->resize_bg = MAX_RESIZE_BG; - else - flex_gd->resize_bg = flexbg_size; + max_resize_bg = umin(flexbg_size, MAX_RESIZE_BG); + flex_gd->resize_bg = max_resize_bg; /* Avoid allocating large 'groups' array if not needed */ last_group = o_group | (flex_gd->resize_bg - 1); if (n_group <= last_group) - flex_gd->resize_bg = 1 << fls(n_group - o_group + 1); + flex_gd->resize_bg = 1 << fls(n_group - o_group); else if (n_group - last_group < flex_gd->resize_bg) - flex_gd->resize_bg = 1 << max(fls(last_group - o_group + 1), + flex_gd->resize_bg = 1 << max(fls(last_group - o_group), fls(n_group - last_group)); + if (WARN_ON_ONCE(flex_gd->resize_bg > max_resize_bg)) + flex_gd->resize_bg = max_resize_bg; + flex_gd->groups = kmalloc_array(flex_gd->resize_bg, sizeof(struct ext4_new_group_data), GFP_NOFS); |