原文 https://balalals.cn/archives/android%E4%B8%ADchmod%E5%A4%B1%E6%95%88

android中chmod失效是因为目录挂载的为noexec属性，可通过mount命查看

rootfs on / type rootfs (ro,seclabel)
tmpfs on /dev type tmpfs (rw,seclabel,nosuid,relatime,size=1384424k,nr_inodes=346106,mode=755)
devpts on /dev/pts type devpts (rw,seclabel,relatime,mode=600)
proc on /proc type proc (rw,relatime,gid=3009,hidepid=2)
sysfs on /sys type sysfs (rw,seclabel,relatime)
selinuxfs on /sys/fs/selinux type selinuxfs (rw,relatime)
tmpfs on /mnt type tmpfs (rw,seclabel,nosuid,nodev,noexec,relatime,size=1384424k,nr_inodes=346106,mode=755,gid=1000)
/dev/block/mmcblk0p61 on /system type ext4 (rw,seclabel,relatime,block_validity,discard,delalloc,barrier,user_xattr)
/dev/block/mmcblk0p62 on /vendor type ext4 (rw,seclabel,relatime,block_validity,discard,delalloc,barrier,user_xattr)
none on /acct type cgroup (rw,nosuid,nodev,noexec,relatime,cpuacct)
debugfs on /sys/kernel/debug type debugfs (rw,seclabel,relatime)
none on /dev/stune type cgroup (rw,nosuid,nodev,noexec,relatime,schedtune)
none on /config type configfs (rw,nosuid,nodev,noexec,relatime)
none on /dev/cpuctl type cgroup (rw,nosuid,nodev,noexec,relatime,cpu)
none on /dev/cpuset type cgroup (rw,nosuid,nodev,noexec,relatime,cpuset,noprefix,release_agent=/sbin/cpuset_release_agent)
cg2_bpf on /dev/cg2_bpf type cgroup2 (rw,nosuid,nodev,noexec,relatime)
pstore on /sys/fs/pstore type pstore (rw,seclabel,nosuid,nodev,noexec,relatime)
none on /sys/fs/cgroup type tmpfs (rw,seclabel,relatime,size=1384424k,nr_inodes=346106,mode=750,gid=1000)
none on /sys/fs/cgroup/freezer type cgroup (rw,relatime,freezer)
tracefs on /sys/kernel/debug/tracing type tracefs (rw,seclabel,relatime)
/dev/block/mmcblk0p63 on /cust type ext4 (ro,seclabel,nosuid,nodev,relatime,data=ordered)
/dev/block/mmcblk0p56 on /vendor/firmware_mnt type vfat (ro,context=u:object_r:firmware_file:s0,relatime,gid=1000,fmask=0337,dmask=0227,codepage=437,iocharset=iso8859-1,shortname=lower,errors=remount-ro)
/dev/block/mmcblk0p38 on /vendor/bt_firmware type vfat (ro,context=u:object_r:bt_firmware_file:s0,relatime,uid=1002,gid=3002,fmask=0337,dmask=0227,codepage=437,iocharset=iso8859-1,shortname=lower,errors=remount-ro)
/dev/block/mmcblk0p48 on /vendor/dsp type ext4 (ro,seclabel,nosuid,nodev,relatime,data=ordered)
/dev/block/mmcblk0p60 on /cache type ext4 (rw,seclabel,nosuid,nodev,noatime,data=ordered)
/dev/block/mmcblk0p53 on /mnt/vendor/persist type ext4 (rw,seclabel,nosuid,nodev,noatime,data=ordered)
tmpfs on /storage type tmpfs (rw,seclabel,nosuid,nodev,noexec,relatime,size=1384424k,nr_inodes=346106,mode=755,gid=1000)
adb on /dev/usb-ffs/adb type functionfs (rw,relatime)
/dev/block/dm-0 on /data type ext4 (rw,lazytime,seclabel,nosuid,nodev,noatime,noauto_da_alloc,resgid=1065,data=ordered)
/data/media on /mnt/runtime/default/emulated type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=1015,multiuser,mask=6,derive_gid,default_normal)
/data/media on /storage/emulated type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=1015,multiuser,mask=6,derive_gid,default_normal)
/data/media on /mnt/runtime/read/emulated type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=9997,multiuser,mask=23,derive_gid,default_normal)
/data/media on /mnt/runtime/write/emulated type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=9997,multiuser,mask=7,derive_gid,default_normal)

带有 noexec 都不可以chmod +x … 或者./a.out 执行任何文件。将可执行文件放入不带noexec 目录下即可。