Fix LD_PRELOAD namespace restriction using memfd#553
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JingMatrix merged 1 commit intomasterfrom Mar 6, 2026
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The Android dynamic linker (Bionic) restricts loading libraries from unauthorized paths via LD_PRELOAD. This causes the linker to reject the hook library with a "not accessible for the namespace" fatal error. To bypass this restriction, we exploit a fallback in Bionic that explicitly skips the namespace accessibility check for files located on tmpfs. We use `memfd_create` to create an anonymous tmpfs-backed file descriptor, copy the library into it using `sendfile`, and pass the new memfd to LD_PRELOAD instead. Reference: function `load_library` in https://cs.android.com/android/platform/superproject/main/+/main:bionic/linker/linker.cpp
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The Android dynamic linker (Bionic) restricts loading libraries from unauthorized paths via LD_PRELOAD. This causes the linker to reject the hook library with a "not accessible for the namespace" fatal error.
To bypass this restriction, we exploit a fallback in Bionic that explicitly skips the namespace accessibility check for files located on tmpfs. We use
memfd_createto create an anonymous tmpfs-backed file descriptor, copy the library into it usingsendfile, and pass the new memfd to LD_PRELOAD instead.Reference: function
load_libraryin https://cs.android.com/android/platform/superproject/main/+/main:bionic/linker/linker.cpp