kernel/linux.git/lib/bootconfig.c, branch v5.10.268

bootconfig: fix NULL-pointer arithmetic in xbc_snprint_cmdline()

2026-08-23T12:16:23+00:00

[ Upstream commit dec4d8118c179b3d12bca7e609054c6011c4f2ce ] xbc_snprint_cmdline() is meant to be called twice: first with buf=NULL, size=0 to probe the rendered length, then with a real buffer to fill it (the standard snprintf() two-pass pattern). The probe call makes the function compute "buf + size" (NULL + 0) and, on every iteration, advance "buf += ret" from that NULL base and pass the result back into snprintf(). Pointer arithmetic on a NULL pointer is undefined behavior. It is harmless in the in-kernel callers today, but the follow-up patches run this same code in the userspace tools/bootconfig parser at kernel build time, where host UBSan / FORTIFY_SOURCE abort the build. Track a running written length (size_t) instead of mutating @buf, and only form "buf + len" when @buf is non-NULL. snprintf(NULL, 0, ...) is itself well defined and returns the would-be length, so the two-pass "probe then fill" usage returns identical byte counts. Link: https://lore.kernel.org/all/20260626-bootconfig_using_tools-v7-1-24ab72139c29@debian.org/ Fixes: 51887d03aca1 ("bootconfig: init: Allow admin to use bootconfig for kernel command line") Cc: stable@vger.kernel.org Signed-off-by: Breno Leitao Signed-off-by: Masami Hiramatsu (Google) Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

bootconfig: move xbc_snprint_cmdline() to lib/bootconfig.c

2026-08-23T12:16:23+00:00

[ Upstream commit 5a643e4623238e14b03d75ca0d4eda0645720cee ] Move xbc_snprint_cmdline() from init/main.c to lib/bootconfig.c so the function (and its xbc_namebuf scratch buffer) becomes part of the shared parser library. tools/bootconfig already compiles lib/bootconfig.c directly, which lets a follow-up patch reuse the same renderer in the userspace tool to convert a bootconfig file into a flat cmdline string at build time. No functional change. Link: https://lore.kernel.org/all/20260508-bootconfig_using_tools-v1-1-1132219aa773@debian.org/ Signed-off-by: Breno Leitao Signed-off-by: Masami Hiramatsu (Google) Stable-dep-of: dec4d8118c17 ("bootconfig: fix NULL-pointer arithmetic in xbc_snprint_cmdline()") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

lib/bootconfig: check bounds before writing in __xbc_open_brace()

2026-04-18T08:30:57+00:00

commit 560f763baa0f2c9a44da4294c06af071405ac46f upstream. The bounds check for brace_index happens after the array write. While the current call pattern prevents an actual out-of-bounds access (the previous call would have returned an error), the write-before-check pattern is fragile and would become a real out-of-bounds write if the error return were ever not propagated. Move the bounds check before the array write so the function is self-contained and safe regardless of caller behavior. Link: https://lore.kernel.org/all/20260312191143.28719-3-objecting@objecting.org/ Fixes: ead1e19ad905 ("lib/bootconfig: Fix a bug of breaking existing tree nodes") Cc: stable@vger.kernel.org Signed-off-by: Josh Law Signed-off-by: Masami Hiramatsu (Google) Signed-off-by: Greg Kroah-Hartman

lib/bootconfig: fix snprintf truncation check in xbc_node_compose_key_after()

2026-04-18T08:30:57+00:00

commit 1120a36bb1e9b9e22de75ecb4ef0b998f73a97f1 upstream. snprintf() returns the number of characters that would have been written excluding the NUL terminator. Output is truncated when the return value is >= the buffer size, not just > the buffer size. When ret == size, the current code takes the non-truncated path, advancing buf by ret and reducing size to 0. This is wrong because the output was actually truncated (the last character was replaced by NUL). Fix by using >= so the truncation path is taken correctly. Link: https://lore.kernel.org/all/20260312191143.28719-4-objecting@objecting.org/ Fixes: 76db5a27a827 ("bootconfig: Add Extra Boot Config support") Cc: stable@vger.kernel.org Signed-off-by: Josh Law Signed-off-by: Masami Hiramatsu (Google) Signed-off-by: Greg Kroah-Hartman

lib/bootconfig: fix off-by-one in xbc_verify_tree() unclosed brace error

2026-04-18T08:30:56+00:00

commit 39ebc8d7f561e1b64eca87353ef9b18e2825e591 upstream. __xbc_open_brace() pushes entries with post-increment (open_brace[brace_index++]), so brace_index always points one past the last valid entry. xbc_verify_tree() reads open_brace[brace_index] to report which brace is unclosed, but this is one past the last pushed entry and contains stale/zero data, causing the error message to reference the wrong node. Use open_brace[brace_index - 1] to correctly identify the unclosed brace. brace_index is known to be > 0 here since we are inside the if (brace_index) guard. Link: https://lore.kernel.org/all/20260312191143.28719-2-objecting@objecting.org/ Fixes: ead1e19ad905 ("lib/bootconfig: Fix a bug of breaking existing tree nodes") Cc: stable@vger.kernel.org Signed-off-by: Josh Law Reviewed-by: Steven Rostedt (Google) Signed-off-by: Masami Hiramatsu (Google) Signed-off-by: Greg Kroah-Hartman

lib/bootconfig: Fix to remove tailing spaces after value

2020-09-22T01:50:09+00:00

Fix to remove tailing spaces after value. If there is a space after value, the bootconfig failed to remove it because it applies strim() before replacing the delimiter with null. For example, foo = var # comment was parsed as below. foo="var " but user will expect foo="var" This fixes it by applying strim() after removing the delimiter. Link: https://lkml.kernel.org/r/160068149134.1088739.8868306567670058853.stgit@devnote2 Fixes: 76db5a27a827 ("bootconfig: Add Extra Boot Config support") Cc: Ingo Molnar Cc: stable@vger.kernel.org Signed-off-by: Masami Hiramatsu Signed-off-by: Steven Rostedt (VMware)

lib/bootconfig: Fix a bug of breaking existing tree nodes

2020-09-22T01:45:52+00:00

Fix a bug of breaking existing tree nodes by parsing the second and subsequent braces. Since the bootconfig parser uses the node.next field as a flag of current parent node, but this will break the existing tree if the same key node is specified again in the bootconfig. For example, the following bootconfig should be foo.buz and bar. foo bar foo { buz } However, when parsing the brace "{", it breaks foo->bar link by marking open-brace node. So the bootconfig unlinks bar from the bootconfig internal tree. This introduces a stack outside of the tree and record the last open-brace on the stack instead of using node.next field. Link: https://lkml.kernel.org/r/160068148267.1088739.8264704338030168660.stgit@devnote2 Fixes: 76db5a27a827 ("bootconfig: Add Extra Boot Config support") Cc: Ingo Molnar Cc: stable@vger.kernel.org Signed-off-by: Masami Hiramatsu Signed-off-by: Steven Rostedt (VMware)

lib: Revert use of fallthrough pseudo-keyword in lib/

2020-08-24T21:17:44+00:00

The following build error for powerpc64 was reported by Nathan Chancellor: "$ scripts/config --file arch/powerpc/configs/powernv_defconfig -e KERNEL_XZ $ make -skj"$(nproc)" ARCH=powerpc CROSS_COMPILE=powerpc64le-linux- distclean powernv_defconfig zImage ... In file included from arch/powerpc/boot/../../../lib/decompress_unxz.c:234, from arch/powerpc/boot/decompress.c:38: arch/powerpc/boot/../../../lib/xz/xz_dec_stream.c: In function 'dec_main': arch/powerpc/boot/../../../lib/xz/xz_dec_stream.c:586:4: error: 'fallthrough' undeclared (first use in this function) 586 | fallthrough; | ^~~~~~~~~~~ This will end up affecting distribution configurations such as Debian and OpenSUSE according to my testing. I am not sure what the solution is, the PowerPC wrapper does not set -D__KERNEL__ so I am not sure that compiler_attributes.h can be safely included." In order to avoid these sort of problems, it seems that the best solution is to use /* fall through */ comments instead of the fallthrough pseudo-keyword macro in lib/, for now. Reported-by: Nathan Chancellor Fixes: df561f6688fe ("treewide: Use fallthrough pseudo-keyword") Signed-off-by: Gustavo A. R. Silva Reviewed-and-tested-by: Nathan Chancellor Signed-off-by: Linus Torvalds

treewide: Use fallthrough pseudo-keyword

2020-08-23T22:36:59+00:00

Replace the existing /* fall through */ comments and its variants with the new pseudo-keyword macro fallthrough[1]. Also, remove unnecessary fall-through markings when it is the case. [1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through Signed-off-by: Gustavo A. R. Silva

lib/bootconfig: Add override operator support

2020-08-03T20:22:28+00:00

Add the value override operator (":=") support to the bootconfig. This value override operator will be useful for the bootloaders which will only update the existing bootconfig according to the bootloader boot options. Without this override operator, the bootloader needs to parse the existing bootconfig and update it. However, with this assignment, it can just append the updated (partial) bootconfig text at the tail of existing one without parsing it. (Of course, it must update the size, checksum and magic, but that will be done easily) Link: https://lkml.kernel.org/r/159482882954.126704.16209517125614438640.stgit@devnote2 Signed-off-by: Masami Hiramatsu Signed-off-by: Steven Rostedt (VMware)