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7c2c7d9930
check_unsafe_exec() also notes whether the fs_struct is being shared by more threads than will get killed by the exec, and if so sets LSM_UNSAFE_SHARE to make bprm_set_creds() careful about euid. But /proc/<pid>/cwd and /proc/<pid>/root lookups make transient use of get_fs_struct(), which also raises that sharing count. This might occasionally cause a setuid program not to change euid, in the same way as happened with files->count (check_unsafe_exec also looks at sighand->count, but /proc doesn't raise that one). We'd prefer exec not to unshare fs_struct: so fix this in procfs, replacing get_fs_struct() by get_fs_path(), which does path_get while still holding task_lock, instead of raising fs->count. Signed-off-by: Hugh Dickins <hugh@veritas.com> Cc: stable@kernel.org ___ fs/proc/base.c | 50 +++++++++++++++-------------------------------- 1 file changed, 16 insertions(+), 34 deletions(-) Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>