From 03c87a1c896c4b7c8797a8af2bbc020998e31c6d Mon Sep 17 00:00:00 2001 From: ZhaoLong Wang Date: Tue, 12 Jul 2022 22:51:59 +0800 Subject: [PATCH] tmpfs: fix the issue that the mount and remount results are inconsistent. hulk inclusion category: bugfix bugzilla: 187184, https://gitee.com/openeuler/kernel/issues/I5G9EK CVE: NA -------------------------------- An undefined-behavior issue has not been completely fixed since commit a70846a97e7b("tmpfs: fix undefined-behaviour in shmem_reconfigure()"). In the commit, check in the shmem_reconfigure() is added in remount process to avoid the Ubsan problem. However, the check is not added to the mount process. It causes inconsistent results between mount and remount. The operations to reproduce the problem in user mode as follows: If nr_blocks is set to 0x8000000000000000, the mounting is successful. # mount tmpfs /dev/shm/ -t tmpfs -o nr_blocks=0x8000000000000000 However, when -o remount is used, the mount fails because of the check in the shmem_reconfigure() # mount tmpfs /dev/shm/ -t tmpfs -o remount,nr_blocks=0x8000000000000000 mount: /dev/shm: mount point not mounted or bad option. Therefore, add checks in the shmem_parse_one() function and remove the check in shmem_reconfigure() to avoid this problem. Signed-off-by: ZhaoLong Wang Reviewed-by: Zhang Yi Signed-off-by: Zheng Zengkai --- mm/shmem.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) diff --git a/mm/shmem.c b/mm/shmem.c index f043682ba567..ad2d68150ed2 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -3432,7 +3432,7 @@ static int shmem_parse_one(struct fs_context *fc, struct fs_parameter *param) break; case Opt_nr_blocks: ctx->blocks = memparse(param->string, &rest); - if (*rest) + if (*rest || ctx->blocks > S64_MAX) goto bad_value; ctx->seen |= SHMEM_SEEN_BLOCKS; break; @@ -3553,10 +3553,7 @@ static int shmem_reconfigure(struct fs_context *fc) spin_lock(&sbinfo->stat_lock); inodes = sbinfo->max_inodes - sbinfo->free_inodes; - if (ctx->blocks > S64_MAX) { - err = "Number of blocks too large"; - goto out; - } + if ((ctx->seen & SHMEM_SEEN_BLOCKS) && ctx->blocks) { if (!sbinfo->max_blocks) { err = "Cannot retroactively limit size"; -- GitLab