5.4-stable review patch. If anyone has any objections, please let me know.
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From: Zijun Hu quic_zijuhu@quicinc.com
[ Upstream commit 1363c134ade81e425873b410566e957fecebb261 ]
fs_name() has @index as unsigned int, so there is underflow risk for operation '@index--'.
Fix by breaking the for loop when '@index == 0' which is also more proper than '@index <= 0' for unsigned integer comparison.
Signed-off-by: Zijun Hu quic_zijuhu@quicinc.com Link: https://lore.kernel.org/20250410-fix_fs-v1-1-7c14ccc8ebaa@quicinc.com Signed-off-by: Christian Brauner brauner@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/filesystems.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-)
--- a/fs/filesystems.c +++ b/fs/filesystems.c @@ -155,15 +155,19 @@ static int fs_index(const char __user * static int fs_name(unsigned int index, char __user * buf) { struct file_system_type * tmp; - int len, res; + int len, res = -EINVAL;
read_lock(&file_systems_lock); - for (tmp = file_systems; tmp; tmp = tmp->next, index--) - if (index <= 0 && try_module_get(tmp->owner)) + for (tmp = file_systems; tmp; tmp = tmp->next, index--) { + if (index == 0) { + if (try_module_get(tmp->owner)) + res = 0; break; + } + } read_unlock(&file_systems_lock); - if (!tmp) - return -EINVAL; + if (res) + return res;
/* OK, we got the reference, so we can safely block */ len = strlen(tmp->name) + 1;