libc/stdio: allocate a buffer in getdelim() when *lineptr is NULL - #20034
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libc/stdio: allocate a buffer in getdelim() when *lineptr is NULL#20034xiaoxiang781216 wants to merge 1 commit into
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POSIX requires getdelim()/getline() to allocate a new buffer whenever *lineptr is NULL, regardless of the value of *n. The previous code read the buffer size from *n unconditionally and only fell back to the initial size when *n was zero, so a caller that passes *lineptr == NULL together with an uninitialized (non-zero) *n caused lib_malloc() to be invoked with that garbage size and typically fail with ENOMEM. Treat a NULL *lineptr the same as a zero *n: (re)allocate from the known BUFSIZE_INIT and ignore the untrusted *n. This matches the glibc behaviour that portable code relies on (for example toybox grep, which calls getdelim() with an uninitialized size variable). Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>
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acassis
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Sep 1, 2026
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@xiaoxiang781216 please include a getdelim() test to apps, git grep getdelim at nuttx-apps returns nothing.
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Summary
POSIX requires
getdelim()/getline()to allocate a new buffer whenever*lineptris NULL, regardless of the value of*n. The previous code read the buffer size from*nunconditionally and only fell back to the initial size when*nwas zero, so a caller that passes*lineptr == NULLtogether with an uninitialized (non-zero)*ncausedlib_malloc()to be invoked with that garbage size and typically fail withENOMEM.Treat a NULL
*lineptrthe same as a zero*n: (re)allocate from the knownBUFSIZE_INITand ignore the untrusted*n. This matches the glibc behaviour that portable code relies on (for example toyboxgrep, which callsgetdelim()with an uninitialized size variable).Impact
libs/libc/stdio/lib_getdelim.c;getline()shares the same implementation and benefits from the same fix.Testing
Built and booted
sim:nshon Linux; verifiedgetline()with*lineptr == NULLand an uninitialized*nnow succeeds instead of returningENOMEM.