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authorHawkins Jiawei2022-10-21 07:16:08 +0800
committerAndrew Morton2022-11-08 17:37:21 -0800
commit26215b7ee923b9251f7bb12c4e5f09dc465d35f2 (patch)
treecf73e24e9e438c3a49f6a003aee7b97bdc57898d
parentb66d00dfebe79ebd0d5a0ec4ee4e26583432c381 (diff)
hugetlbfs: fix null-ptr-deref in hugetlbfs_parse_param()
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: <TASK> 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 [...] </TASK> ====================================================== According to commit "vfs: parse: deal with zero length string value", kernel will set 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(). Link: https://lkml.kernel.org/r/20221020231609.4810-1-yin31149@gmail.com 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 <yin31149@gmail.com> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com> Cc: Hawkins Jiawei <yin31149@gmail.com> Cc: Muchun Song <songmuchun@bytedance.com> Cc: Ian Kent <raven@themaw.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
-rw-r--r--fs/hugetlbfs/inode.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 00495fc128c5..09e644f80a4a 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -1378,7 +1378,7 @@ 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;
@@ -1388,7 +1388,7 @@ 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;
@@ -1404,7 +1404,7 @@ 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;