From: ZhaoLong Wang wangzhaolong1@huawei.com
hulk inclusion category: bugfix bugzilla: 187184, https://gitee.com/openeuler/kernel/issues/I5G9EK CVE: NA
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An undefined-behavior issue has not been completely fixed since commit 5f62fbf88c99("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 wangzhaolong1@huawei.com Reviewed-by: Zhang Yi yi.zhang@huawei.com Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com --- 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";